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    AuthorTitleYearJournal/ProceedingsReftypeDOI/URL
    Antoniou, G., Bikakis, A., Dimaresis, N., Genetzakis, M., Georgalis, G., Governatori, G., Karouzaki, E., Kazepis, N., Kosmadakis, D., Kritsotakis, M., Lilis, G., Papadogiannakis, A., Pediaditis, P., Terzakis, C., Theodosaki, R. & Zeginis, D. Proof Explanation for the Semantic Web Using Defeasible Logic 2007 Knowledge Science, Engineering and Management, pp. 186-197  inproceedings DOI  
    Abstract: In this work we present the design and implementation of a system for proof explanation in the Semantic Web, based on defeasible reasoning. Trust is a vital feature for Semantic Web. If users (humans and agents) are to use and integrate system answers, they must trust them. Thus, systems should be able to explain their actions, sources, and beliefs. Our system produces automatically proof explanations using a popular logic programming system (XSB), by interpreting the output from the proof's trace and converting it into a meaningful representation. It also supports an XML representation (a RuleML language extension) for agent communication, which is a common scenario in the Semantic Web. The system in essence implements a proof layer for nonmonotonic rules on the Semantic Web.
    BibTeX:
    @inproceedings{ksem07,
      author = {Antoniou, Grigoris and Bikakis, Antonis and Dimaresis, Nikos and Genetzakis, Manolis and Georgalis, Giannis and Governatori, Guido and Karouzaki, Efie and Kazepis, Nikolas and Kosmadakis, Dimitris and Kritsotakis, Manolis and Lilis, Giannis and Papadogiannakis, Antonis and Pediaditis, Panagiotis and Terzakis, Constantinos and Theodosaki, Rena and Zeginis, Dimitris},
      title = {Proof Explanation for the Semantic Web Using Defeasible Logic},
      booktitle = {Knowledge Science, Engineering and Management},
      publisher = {Springer},
      year = {2007},
      pages = {186-197},
      doi = {http://dx.doi.org/10.1007/978-3-540-76719-0_21}
    }
    
    Antoniou, G., Bikakis, A., Dimaresis, N., Genetzakis, M., Georgalis, G., Governatori, G., Karouzaki, E., Kazepis, N., Kosmadakis, D., Kritsotakis, M., Lilis, G., Papadogiannakis, A., Pediaditis, P., Terzakis, C., Theodosaki, R. & Zeginis, D. Proof explanation for a nonmonotonic Semantic Web rules language 2008 Data & Knowledge Engineering
    Vol. 64 (3) , pp. 662-687 
    article DOI  
    Abstract: In this work, we present the design and implementation of a system for proof explanation in the Semantic Web, based on defeasible reasoning. Trust is a vital feature for Semantic Web. If users (humans and agents) are to use and integrate system answers, they must trust them. Thus, systems should be able to explain their actions, sources, and beliefs. Our system produces automatically proof explanations using a popular logic programming system (XSB), by interpreting the out- put from the proof’s trace and converting it into a meaningful representation. It also supports an XML representation for agent communication, which is a common scenario in the Semantic Web. In this paper, we present the design and implementation of the system, a RuleML language extension for the representation of a proof explanation, and we give some examples of the system. The system in essence implements a proof layer for nonmonotonic rules on the Semantic Web.
    BibTeX:
    @article{dke:proof,
      author = {Antoniou, Grigoris and Bikakis, Antonis and Dimaresis, Nikos and Genetzakis, Manolis and Georgalis, Giannis and Governatori, Guido and Karouzaki, Efie and Kazepis, Nikolas and Kosmadakis, Dimitris and Kritsotakis, Manolis and Lilis, Giannis and Papadogiannakis, Antonis and Pediaditis, Panagiotis and Terzakis, Constantinos and Theodosaki, Rena and Zeginis, Dimitris},
      title = {Proof explanation for a nonmonotonic Semantic Web rules language},
      journal = {Data & Knowledge Engineering},
      year = {2008},
      volume = {64},
      number = {3},
      pages = {662-687},
      doi = {http://dx.doi.org/10.1016/j.datak.2007.10.006}
    }
    
    Antoniou, G., Billington, D., Governatori, G. & Maher, M. J. Embedding Defeasible Logic into Logic Programming 2006 Theory and Practice of Logic Programming
    Vol. 6 (6) , pp. 703-735 
    article DOI  
    Abstract: Defeasible reasoning is a simple but efficient approach to nonmonotonic reasoning that has recently attracted considerable interest and that has found various applications. Defeasible logic and its variants are an important family of defeasible reasoning methods. So far no relationship has been established between defeasible logic and mainstream nonmonotonic reasoning approaches. In this paper we establish close links to known semantics of logic programs. In particular, we give a translation of a defeasible theory $D$ into a meta-program $P(D)$. We show that under a condition of decisiveness, the defeasible consequences of $D$ correspond exactly to the sceptical conclusions of $P(D)$ under the stable model semantics. Without decisiveness, the result holds only in one direction (all defeasible consequences of $D$ are included in all stable models of $P(D)$). If we wish a complete embedding for the general case, we need to use the Kunen semantics of $P(D)$, instead.
    BibTeX:
    @article{tplp:embedding,
      author = {Antoniou, Grigoris and Billington, David and Governatori, Guido and Maher, Michael J.},
      title = {Embedding Defeasible Logic into Logic Programming},
      journal = {Theory and Practice of Logic Programming},
      year = {2006},
      volume = {6},
      number = {6},
      pages = {703-735},
      doi = {http://dx.doi.org/10.1017/S1471068406002778}
    }
    
    Antoniou, G., Billington, D., Governatori, G. & Maher, M. J. Representation Results for Defeasible Logic 2001 ACM Transactions on Computational Logic
    Vol. 2 (2) , pp. 255-287 
    article DOI  
    Abstract: The importance of transformations and normal forms in logic programming, and generally in computer science, is well documented. This paper investigates transformations and normal forms in the context of Defeasible Logic, a simple but efficient formalism for nonmonotonic reasoning based on rules and priorities. The transformations described in this paper have two main benefits: on one hand they can be used as a theoretical tool that leads to a deeper understanding of the formalism, and on the other hand they have been used in the development of an efficient implementation of defeasible logic.
    BibTeX:
    @article{tocl,
      author = {Antoniou, Grigoris and Billington, David and Governatori, Guido and Maher, Michael J.},
      title = {Representation Results for Defeasible Logic},
      journal = {ACM Transactions on Computational Logic},
      year = {2001},
      volume = {2},
      number = {2},
      pages = {255-287},
      doi = {http://dx.doi.org/10.1145/371316.371517}
    }
    
    Antoniou, G., Billington, D., Governatori, G. & Maher, M. J. A flexible framework for defeasible logics 2000 Proc. American National Conference on Artificial Intelligence (AAAI-2000), pp. 401-405  inproceedings URL  
    Abstract: Logics for knowledge representation suffer from over-specialization: while each logic may provide an ideal representation formalism for some problems, it is less than optimal for others. A solution to this problem is to choose from several logics and, when necessary, combine the representations. In general, such an approach results in a very difficult problem of combination. However, if we can choose the logics from a uniform framework then the problem of combining them is greatly simplified. In this paper, we develop such a framework for defeasible logics. It supports all defeasible logics that satisfy a strong negation principle. We use logic meta-programs as the basis for the framework.
    BibTeX:
    @inproceedings{aaai2000,
      author = {Antoniou, Grigoris and Billington, David and Governatori, Guido and Maher, Michael J.},
      title = {A flexible framework for defeasible logics},
      booktitle = {Proc. American National Conference on Artificial Intelligence (AAAI-2000)},
      publisher = {AAAI/MIT Press},
      year = {2000},
      pages = {401-405},
      url = {http://www.aaai.org/Press/Proceedings/AAAI/2000/aaai2000.html}
    }
    
    Antoniou, G., Billington, D., Governatori, G. & Maher, M. J. A flexible framework for defeasible logics 2000 Proceeding of the 9$^th$ Workshop on Non-Monotonic Reasoning  inproceedings URL  
    Abstract: Logics for knowledge representation suffer from over-specialization: while each logic may provide an ideal representation formalism for some problems, it is less than optimal for others. A solution to this problem is to choose from several logics and, when necessary, combine the representations. In general, such an approach results in a very difficult problem of combination. However, if we can choose the logics from a uniform framework then the problem of combining them is greatly simplified. In this paper, we develop such a framework for defeasible logics. It supports all defeasible logics that satisfy a strong negation principle. We use logic meta-programs as the basis for the framework.
    BibTeX:
    @inproceedings{nmr,
      author = {Antoniou, Grigoris and Billington, David and Governatori, Guido and Maher, Michael J.},
      title = {A flexible framework for defeasible logics},
      booktitle = {Proceeding of the 9$^th$ Workshop on Non-Monotonic Reasoning},
      year = {2000},
      url = {http://arXiv.org/cs.AI/0004013}
    }
    
    Antoniou, G., Billington, D., Governatori, G. & Maher, M. J. On the Modeling and Analysis of Regulations 1999 Proceedings of the Australian Conference Information Systems, pp. 20-29  inproceedings URL  
    Abstract: Regulations are a wide-spread and important part of government and business. They codify how products must be made and processes should be performed. Such regulations can be difficult to understand and apply. In an environment of growing complexity of, and change in, regulation, automated support for reasoning with regulations is becoming increasingly necessary. In this paper we report on ongoing work which aims at providing automated support for the drafting and use of regulations using logic modelling techniques. We highlight the support that can be provided by logic modelling, describe the technical foundation of our project, and report on the status of the project and the next steps.
    BibTeX:
    @inproceedings{acis,
      author = {Antoniou, Grigoris and Billington, David and Governatori, Guido and Maher, Michael J.},
      title = {On the Modeling and Analysis of Regulations},
      booktitle = {Proceedings of the Australian Conference Information Systems},
      year = {1999},
      pages = {20-29},
      url = {http://www.vuw.ac.nz/acis99/Papers/PaperGovernatori-088.pdf}
    }
    
    Antoniou, G., Billington, D., Governatori, G., Maher, M. J. & Rock, A. A Family of Defeasible Reasoning Logics and its Implementation 2000 ECAI 2000. Proceedings of the 14th European Conference on Artificial Intelligence, pp. 459-463  inproceedings  
    Abstract: Defeasible reasoning is a direction in nonmonotonic reasoning that is based on the use of rules that may be defeated by other rules. It is a simple, but often more efficient approach than other nonmonotonic reasoning systems. This paper presents a family of defeasible reasoning formalisms built around Nute's defeasible logic. We describe the motivations of these formalisms and derive some basic properties and interrelationships. We also describe a query answering system that supports these formalisms and is available on the World Wide Web.
    BibTeX:
    @inproceedings{ecai2000-5,
      author = {Antoniou, Grigoris and Billington, David and Governatori, Guido and Maher, Michael J. and Rock, Andrew},
      title = {A Family of Defeasible Reasoning Logics and its Implementation},
      booktitle = {ECAI 2000. Proceedings of the 14th European Conference on Artificial Intelligence},
      publisher = {IOS Press},
      year = {2000},
      pages = {459-463}
    }
    
    Antoniou, G., Dimaresis, N. & Governatori, G. A System for Modal and Deontic Defeasible Reasoning 2007 20th Australian Joint Conference on Artificial Intelligence, AI 2007, pp. 609-613  inproceedings DOI  
    Abstract: Defeasible reasoning is a well-established nonmonotonic reasoning approach that has recently been combined with semantic web technologies. This paper describes modal and deontic extensions of defeasible logic, motivated by potential applications for modelling multi-agent systems and policies. It describes a logic metaprogram that captures the underlying intuitions, and outlines an implemented system.
    BibTeX:
    @inproceedings{austai07:modal,
      author = {Antoniou, Grigoris and Dimaresis, Nikos and Governatori, Guido},
      title = {A System for Modal and Deontic Defeasible Reasoning},
      booktitle = {20th Australian Joint Conference on Artificial Intelligence, AI 2007},
      publisher = {Springer},
      year = {2007},
      pages = {609-613},
      doi = {http://dx.doi.org/10.1007/978-3-540-76928-6_62}
    }
    
    Antoniou, G., Dimaresis, N. & Governatori, G. A system for modal and deontic defeasible reasoning 2008 Proceedings of the 2008 ACM Symposium on Applied Computing, pp. 2261-2265  inproceedings DOI  
    Abstract: Defeasible reasoning is a well-established nonmonotonic reasoning approach that has recently been combined with semantic web technologies. This paper describes modal and deontic extensions of defeasible logic, and shows how these extensions can be used for modelling multi-agent systems and policies.
    BibTeX:
    @inproceedings{sac08,
      author = {Antoniou, Grigoris and Dimaresis, Nikos and Governatori, Guido},
      title = {A system for modal and deontic defeasible reasoning},
      booktitle = {Proceedings of the 2008 ACM Symposium on Applied Computing},
      publisher = {ACM},
      year = {2008},
      pages = {2261-2265},
      doi = {http://doi.acm.org/10.1145/1363686.1364226}
    }
    
    Antoniou, G., Dimaresis, N. & Governatori, G. A Modal and Deontic Defeasible Reasoning System for Modelling Policies and Multi-Agent Systems 2009 Expert Systems With Applications
    Vol. 36 (2) , pp. 4125-4134 
    article DOI  
    BibTeX:
    @article{AntDimGov:eswa:modal,
      author = {Antoniou, Grigoris and Dimaresis, Nikos and Governatori, Guido},
      title = {A Modal and Deontic Defeasible Reasoning System for Modelling Policies and Multi-Agent Systems},
      journal = {Expert Systems With Applications},
      year = {2009},
      volume = {36},
      number = {2},
      pages = {4125-4134},
      doi = {http://dx.doi.org/10.1016/j.eswa.2008.03.009}
    }
    
    Antoniou, G., Maher, M. J., Billington, D. & Governatori, G. Comparison of Sceptical NAF-Free Logic Programming Approaches 1999 Logic Programming and Non-monotonic Reasoning, pp. 347-356  inproceedings URL  
    Abstract: Recently there has been increased interest in logic programming-based default reasoning approaches which are not using negation-as-failure in their object language. Instead, default reasoning is modelled by rules and a priority relation among them. Historically the first logic in this class was Defeasible Logic. In this paper we will study its relationship to other approaches which also rely on the idea of using logic rules and priorities. In particular we will study sceptical LPwNF, courteous logic programs, and priority logic.
    BibTeX:
    @inproceedings{lpnmr,
      author = {Antoniou, Grigoris and Maher, Michael J. and Billington, David and Governatori, Guido},
      title = {Comparison of Sceptical NAF-Free Logic Programming Approaches},
      booktitle = {Logic Programming and Non-monotonic Reasoning},
      publisher = {Springer-Verlag},
      year = {1999},
      pages = {347-356},
      url = {http://springerlink.metapress.com/index/XT39RUCLE20BA48F}
    }
    
    Artosi, A., Benassi, P., Governatori, G. & Rotolo, A. Labelled proofs for quantified modal logic 1996 Logics in Artificial Intelligence, pp. 70-86  inproceedings  
    Abstract: In this paper we describe a modal proof system arising from the combination of a tableau-like classical system, which incorporates a restricted (``analytic'') version of the cut rule, with a label formalism which allows for a specialised, logic-dependent unification algorithm. The system provides a uniform proof-theoretical treatment of first-order (normal) modal logics with and without the Barcan Formula and/or its converse.
    BibTeX:
    @inproceedings{jelia,
      author = {Artosi, Alberto and Benassi, Paola and Governatori, Guido and Rotolo, Antonino},
      title = {Labelled proofs for quantified modal logic},
      booktitle = {Logics in Artificial Intelligence},
      publisher = {Springer-Verlag},
      year = {1996},
      pages = {70-86}
    }
    
    Artosi, A., Benassi, P., Governatori, G. & Rotolo, A. Shakespearian modal logic: A Labelled Treatment of Modal Identity 1998 Advances in Modal Logic. Volume 1, pp. 1-21  incollection URL  
    Abstract: In this paper we describe a modal proof system arising from the combination of a tableau-like classical system, which incorporates a restricted (``analytical'') version of the cut rule, with a label formalism which allows for a specialised, logic dependant unification algorithm. The system provides a uniform proof-theoretical treatment of first-order (normal) modal logics with identity, with and without Barcan formula and/or its converse
    BibTeX:
    @incollection{advances,
      author = {Artosi, Alberto and Benassi, Paola and Governatori, Guido and Rotolo, Antonino},
      title = {Shakespearian modal logic: A Labelled Treatment of Modal Identity},
      booktitle = {Advances in Modal Logic. Volume 1},
      publisher = {CSLI Publications},
      year = {1998},
      pages = {1-21},
      url = {http://cslipublications.stanford.edu/site/157586102X.html}
    }
    
    Artosi, A., Cattabriga, P. & Governatori, G. A Prolog Implementation of KEM 1995 Proceedings of GULP-PRODE'95, pp. 395-400  inproceedings  
    Abstract: In this paper, we describe a Prolog implementation of a new theorem prover for (normal propositional) modal and multi--modal logics. The theorem prover, which is called $KEM$, arises from the combination of a classical refutation system which incorporates a restricted (``analytic'') version of the cut rule with a label formalism which allows for a specialised logic--dependent unification algorithm. An essential feature of $KEM$ is that it yields a rather simple and efficient proof search procedure which offers many computational advantages over the usual tableau-based proof search methods. This is due partly to the use of linear 2--premise $ rules in place of the branching $ rules of the standard tableau method, and partly to the crucial role played by the analytic cut (the only branching rule) in eliminating redundancy from the search space. It turns out that $KEM$ method of proof search is not only computationally more efficient but also intuitivelly more natural than other (e.g. resolution-based) methods leading to simple and easy implementable procedures (two $KEM$ Theorem Prover-like systems have been implemented: an LPA interpreter on Macintosh, and a Quintus compiler on Sun-Sparcstation) which make it well suited for efficient automated proof search in modal logic.
    BibTeX:
    @inproceedings{gulp,
      author = {Artosi, Alberto and Cattabriga, Paola and Governatori, Guido},
      title = {A Prolog Implementation of KEM},
      booktitle = {Proceedings of GULP-PRODE'95},
      publisher = {Università di Salerno},
      year = {1995},
      pages = {395-400}
    }
    
    Artosi, A., Cattabriga, P. & Governatori, G. KED: A Deontic Theorem Prover 1994 Workshop on Legal Application of Logic Programming, pp. 60-76  inproceedings  
    Abstract: Deontic logic (DL) is increasingly recognized as an indispensable tool in such application areas as formal representation of legal knowledge and reasoning, formal specification of computer systems and formal analysis of database integrity constraints. Despite this acknowledgement, there have been few attempts to provide computationally tractable inference mechanisms for DL. In this paper we shall be concerned with providing a computationally oriented proof method for standard DL (SDL), i.e., normal systems of modal logic with the usual possible-worlds semantics. Because of the natural and easily implementable style of proof construction it uses, this method seems particularly well-suited for applications in the AI and Law field, and though in the present version it works for SDL only, it forms an appropriate basis for developing efficient proof methods for more expressive and sophisticated extensions of SDL.
    BibTeX:
    @inproceedings{ACG94a,
      author = {Artosi, Alberto and Cattabriga, Paola and Guido Governatori},
      title = {KED: A Deontic Theorem Prover},
      booktitle = {Workshop on Legal Application of Logic Programming},
      publisher = {IDG},
      year = {1994},
      pages = {60-76}
    }
    
    Artosi, A., Cattabriga, P. & Governatori, G. An Automated Approach to Normative Reasoning 1994 Artificial Normative Reasoning, pp. 132-145  inproceedings  
    Abstract: It is by now generally accepted in the Artificial Intelligence and Law field that many aspects of normative language and reasoning can be modelled in deontic logics based on modal logic. This obviously implies the need for computationally tractable inference mechanisms for Deontic Logic. In this paper we shall be concerned with developing a computationally oriented proof method for several normal (in Åqvist classification normal and strongly normal) deontic logics. Since this method is arguably more natural and intuitive than other (e.g. resolution or translation based) proof methods, and it leads to simple and easy implementable procedures, it seems particularly well-suited for applications in the newly developed area of ``artificial normative reasoning''. Moreover, though in the present version it works for deontic logics of the simplest kind, it is sufficiently generic and flexible to provide an appropriate algorithmic proof framework for deontic logics of greater richness and complexity.
    BibTeX:
    @inproceedings{ACG94b,
      author = {Artosi, Alberto and Cattabriga, Paola and Guido Governatori},
      title = {An Automated Approach to Normative Reasoning},
      booktitle = {Artificial Normative Reasoning},
      year = {1994},
      pages = {132-145}
    }
    
    Artosi, A., Cattabriga, P. & Governatori, G. A Modal Computational Framework for Default Reasoning 1997 Proceedings of KI-97, pp. 373-376  inproceedings  
    Abstract: Usually a default rule A : B/C is intended to mean that if A holds in a state of affairs a B is consistent, then C follows by default. However, C is not a necessary conclusion: different states of affairs are possible (conceivable). According to this view, Meyer and van der Hoek developed a multimodal logic, called S5P(n), for treating non-monotonic reasoning in a monotonic setting. In this paper we shall describe a proof search algorithm for S5P(n) which has been implemented as a Prolog Interpreter.
    BibTeX:
    @inproceedings{ki97,
      author = {Artosi, Alberto and Cattabriga, Paola and Guido Governatori},
      title = {A Modal Computational Framework for Default Reasoning},
      booktitle = {Proceedings of KI-97},
      publisher = {Springer-Verlag},
      year = {1997},
      pages = {373-376}
    }
    
    Artosi, A. & Governatori, G. Modal Tableaux for Nonmonotonic Reasoning 1998 Prospettive della logica e della filosofia della scienza, pp. 203-213  inproceedings  
    Abstract: The tableau-like proof system KEM has been proven to be able to cope with a wide variety of (normal) modal logics. KEM is based on D'Agostino and Mondadori's (1994) classical proof system KE, a combination of tableau and natural deduction inference rules which allows for a restricted (``analytic'') Use of the cut rule. The key feature of KEM, besides its being based neither on resolution nor on standard sequent/tableau inference techniques, is that it generates models and checks them using a label scheme to bookkeep ``world'' paths. This formalism can be extended to handle various system of multimodal logic devised for dealing with nonmonotonic reasoning, by relying in particular on Meyer and van der Hoek's (1992) logic for actuality and preference. In this paper we shall be concerned with developing a similar extension this time by relying on Schwind and Siegel's (1993,1994) system H, another multimodal logic devised for dealing with nonmonotonic inference.
    BibTeX:
    @inproceedings{silfs,
      author = {Artosi, Alberto and Governatori, Guido},
      title = {Modal Tableaux for Nonmonotonic Reasoning},
      booktitle = {Prospettive della logica e della filosofia della scienza},
      publisher = {ETS},
      year = {1998},
      pages = {203-213}
    }
    
    Artosi, A. & Governatori, G. Popper on Necessity and Natural Laws 2006 Karl Popper Philosopher of Science, pp. 107-118  incollection  
    Abstract: During his philosophical career Popper sought to characterize natural laws alternately as strictly universal and as `naturally' or `physically' necessary statements. In this paper we argue that neither characterization does what Popper claimed and sketch a reconstruction of his views that avoids some of their major drawbacks.
    BibTeX:
    @incollection{artgov:06:popper,
      author = {Artosi, Alberto and Governatori, Guido},
      title = {Popper on Necessity and Natural Laws},
      booktitle = {Karl Popper Philosopher of Science},
      publisher = {Rubbettino Editore},
      year = {2006},
      pages = {107-118}
    }
    
    Artosi, A. & Governatori, G. A tableaux methodology for deontic conditional logics 1998 $EON'98, 4$^th$ International Workshop on Deontic Logic in Computer Science, pp. 65-81  inproceedings URL  
    Abstract: In this paper we present a theorem proving methodology for a restricted but significant fragment of the conditional language made up of (boolean combinations of) conditional statements with unnested antecedents. The method is based on the possible world semantics for conditional logics. The label formalism introduced in tecade,jelia to account for the semantics of normal modal logics is easily adapted to the semantics of conditional logics by simply indexing labels with formulas. The inference rules are provided by the propositional system $KE^+$ --- a tableau-like analytic proof system devised to be used both as a refutation and a direct method of proof --- enlarged with suitable elimination rules for the conditional connective. The theorem proving methodology we are going to present can be viewed as a first step towards developing an appropriate algorithmic framework for several conditional logics for (defeasible) conditional obligation.
    BibTeX:
    @inproceedings{deon,
      author = {Artosi, Alberto and Governatori, Guido},
      title = {A tableaux methodology for deontic conditional logics},
      booktitle = {$EON'98, 4$^th$ International Workshop on Deontic Logic in Computer Science},
      publisher = {CIRFID},
      year = {1998},
      pages = {65-81},
      url = {http://arXiv.org/cs.LO/0003050}
    }
    
    Artosi, A., Governatori, G. & Rotolo, A. A Labelled Tableau Calculus for Nonmonotonic (Cumulative) Consequence Relations 2000 Automated Reasoning with Analytic Tableaux and Related Methods, pp. 82-97  inproceedings URL  
    Abstract: In this paper we present a labelled proof method for computing nonmonotonic consequence relations in a conditional logic setting. The method is based on the usual possible world semantics for conditional logic. The label formalism $KEM$, introduced to account for the semantics of normal modal logics, is easily adapted to the semantics of conditional logic by simply indexing labels with formulas. The inference rules are provided by the propositional system $KE^+$ ---a tableau-like analytic proof system devised to be used both as a refutation and a direct method of proof--- enlarged with suitable elimination rules for the conditional connective. The resulting algorithmic framework is able to compute cumulative consequence relations in so far as they can be expressed as conditional implications.
    BibTeX:
    @inproceedings{tab2000,
      author = {Artosi, Alberto and Governatori, Guido and Antonino Rotolo},
      title = {A Labelled Tableau Calculus for Nonmonotonic (Cumulative) Consequence Relations},
      booktitle = {Automated Reasoning with Analytic Tableaux and Related Methods},
      publisher = {Springer-Verlag},
      year = {2000},
      pages = {82-97},
      url = {http://www.springer.de/comp/lncs/index.html}
    }
    
    Artosi, A., Governatori, G. & Rotolo, A. Labelled Tableaux for Non-monotonic Reasoning: Cumulative Consequence Relations 2002 Journal of Logic and Computation
    Vol. 12 (6) , pp. 1027-1060 
    article DOI  
    Abstract: In this paper we present a labelled proof method for computing nonmonotonic consequence relations in a conditional logic setting. The method exploits the strong connection between these deductive relations and conditional logics, and it is based on the usual possible world semantics devised for the latter. The label formalism introduced to account for the semantics of normal modal logics, is easily adapted to the semantics of conditional logic by simply indexing labels with formulas. The basic inference rules are provided by the propositional system $+$ ---a tableau-like analytic proof system devised to be used both as a refutation method and a direct method of proof--- that is the classical core of KEM which is thus enlarged with suitable elimination rules for the conditional connective. The resulting algorithmic framework is able to compute cumulative consequence relations in so far as they can be expressed as conditional implications.
    BibTeX:
    @article{jlc,
      author = {Artosi, Alberto and Governatori, Guido and Rotolo, Antonino},
      title = {Labelled Tableaux for Non-monotonic Reasoning: Cumulative Consequence Relations},
      journal = {Journal of Logic and Computation},
      year = {2002},
      volume = {12},
      number = {6},
      pages = {1027-1060},
      doi = {http://dx.doi.org/10.1093/logcom/12.6.1027}
    }
    
    Artosi, A., Governatori, G. & Sartor, G. Towards a Computational Treatment of Deontic Defeasibility 1996 Deontic Logic Agency and Normative Systems, pp. 27-46  inproceedings  
    Abstract: In this paper we describe an algorithmic framework for a multi-modal logic arising from the combination of the system of modal (epistemic) logic devised by Meyer and van der Hoek for dealing with nonmonotonic reasoning with a deontic logic of the Jones and Pörn-type. The idea behind this (somewhat eclectic) formal set-up is to have a modal framework expressive enough to model certain kinds of deontic defeasibility, in particular by taking into account preferences on norms. The appropriate inference mechanism is provided by a tableau-like modal theorem proving system which supports a proof method closely related to the semantics of modal operators. We argue that this system is particularly well-suited for mechanizing nonmonotonic forms of inference in a monotonic multi-modal setting.
    BibTeX:
    @inproceedings{AGS96,
      author = {Artosi, Alberto and Governatori, Guido and Sartor, Giovanni},
      title = {Towards a Computational Treatment of Deontic Defeasibility},
      booktitle = {Deontic Logic Agency and Normative Systems},
      publisher = {Springer-Verlag},
      year = {1996},
      pages = {27-46}
    }
    
    Bartolini, C., Governatori, G. & Milosevic, Z. Introduction to the Special Issue: Electronic Contract Architectures and Languages 2008 International Journal of Electronic Commerce
    Vol. 12 (4) , pp. 5-7 
    article DOI  
    BibTeX:
    @article{ijec08:editorial,
      author = {Bartolini, Claudio and Governatori, Guido and Milosevic, Zoran},
      title = {Introduction to the Special Issue: Electronic Contract Architectures and Languages},
      journal = {International Journal of Electronic Commerce},
      year = {2008},
      volume = {12},
      number = {4},
      pages = {5-7},
      doi = {http://dx.doi.org/10.2753/JEC1086-4415120400}
    }
    
    Bassiliades, N., Antoniou, G. & Governatori, G. Proof Explanation in the DR-DEVICE System 2007 Web Reasoning and Rule Systems, pp. 249-258  inproceedings DOI  
    Abstract: Trust is a vital feature for the Semantic Web: If users (humans and agents) are to use and integrate system answers, they must trust them. Thus, systems should be able to explain their actions, sources, and beliefs, and this issue is the topic of the proof layer in the design of the Semantic Web. This paper presents the design of a system for proof explanation on the Semantic Web, based on defeasible reasoning. The basis of this work is the DR-DEVICE system that is extended to handle proofs. A critical aspect is the representation of proofs in an XML language, which is achieved by a RuleML language extension.
    BibTeX:
    @inproceedings{rr07:proof,
      author = {Bassiliades, Nick and Antoniou, Grigoris and Governatori, Guido},
      title = {Proof Explanation in the DR-DEVICE System},
      booktitle = {Web Reasoning and Rule Systems},
      publisher = {Springer},
      year = {2007},
      pages = {249-258},
      doi = {http://dx.doi.org/10.1007/978-3-540-72982-2_19}
    }
    
    Bassiliades, N., Governatori, G., Paschke, A. & Dix, Jü. Guest Editors' Introduction: Rule Representation, Interchange, and Reasoning in Distributed, Heterogeneous Environments 2010 IEEE Transaction on Knowledge and Data Engineering
    Vol. 22 (11) , pp. 1489-1491 
    article DOI  
    BibTeX:
    @article{tkde2010,
      author = {Nick Bassiliades and Guido Governatori and Adrian Paschke and Jürgen Dix},
      title = {Guest Editors' Introduction: Rule Representation, Interchange, and Reasoning in Distributed, Heterogeneous Environments},
      journal = {IEEE Transaction on Knowledge and Data Engineering},
      year = {2010},
      volume = {22},
      number = {11},
      pages = {1489-1491},
      doi = {http://dx.doi.org/10.1109/TKDE.2010.179}
    }
    
    Billington, D., Antoniou, G., Governatori, G. & Maher, M. J. Revising Nonmonotonic Belief Sets: The Case of Defeasible Logic 1999 KI-99: Advances in Artificial Intelligence, pp. 101-112  inproceedings URL  
    Abstract: The revision and transformation of knowledge is widely recognized as a key issue in knowledge representation and reasoning. Reasons for the importance of this topic are the fact that intelligent systems are gradually developed and refined, and that often the environment of an intelligent system is not static but changes over time. Traditionally belief revision has been concerned with revising first order theories. Nonmonotonic reasoning provides rigorous techniques for reasoning with incomplete information. Until recently the dynamics of nonmonotonic reasoning approaches has attracted little attention. This paper studies the dynamics of defeasible logic, a simple and efficient form of nonmonotonic reasoning based on defeasible rules and priorities. We define revision and contraction operators, propose postulates motivated by the form or the intuition of the AGM postulates for classical belief revision, and verify that the operators satisfy the postulates.
    BibTeX:
    @inproceedings{ki99,
      author = {Billington, David and Antoniou, Grigoris and Governatori, Guido and Maher, Michael J.},
      title = {Revising Nonmonotonic Belief Sets: The Case of Defeasible Logic},
      booktitle = {KI-99: Advances in Artificial Intelligence},
      publisher = {Springer-Verlag},
      year = {1999},
      pages = {101-112},
      url = {http://www.springer.de/comp/lncs/index.html}
    }
    
    Billington, D., Antoniou, G., Governatori, G. & Maher, M. J. An Inclusion Theorem for Defeasible Logic ACM Transactions in Computational Logic   article URL  
    Abstract: Defeasible reasoning is a computationally simple nonmonotonic reasoning approach that has attracted significant theoretical and practical attention. It comprises a family of logics that capture different intuitions, among them ambiguity propagation versus ambiguity blocking, and the adoption or rejection of team defeat. This paper provides a compact presentation of the defeasible logic variants, and derives an Inclusion Theorem which shows that different notions of provability in defeasible logic form a chain of levels of proof.
    BibTeX:
    @article{tocl:inclusion,
      author = {Billington, David and Antoniou, Grigoris and Governatori, Guido and Maher, Michael J.},
      title = {An Inclusion Theorem for Defeasible Logic},
      journal = {ACM Transactions in Computational Logic},
      url = {http://tocl.acm.org/accepted/370antoniou.pdf}
    }
    
    Blee, J., Billington, D., Governatori, G. & Sattar, A. Levels of Modalities for BDI Logic 2008 2008 IEEE/WIC/ACM International Conference on Web Intelligence and Intelligent Agent Technology, pp. 647-650  inproceedings DOI  
    Abstract: The use of rational agents for modelling real world problems has both been heavily investigated and become well accepted, with BDI Logic being a widely used architecture to represent and reason about rational agency. However, in the real world, we often have to deal with different levels of confidence in our beliefs, desires, and intentions. This paper extends our previous framework that integrated qualitative levels into BDI Logic. We describe an expanded set of axioms and properties of the extended logic and also define a detailed non-normal Kripke type semantics.
    BibTeX:
    @inproceedings{wliamas08:blee,
      author = {Blee, Jeff and Billington, David and Governatori, Guido and Sattar, Abdul},
      title = {Levels of Modalities for BDI Logic},
      booktitle = {2008 IEEE/WIC/ACM International Conference on Web Intelligence and Intelligent Agent Technology},
      publisher = {IEEE Press},
      year = {2008},
      pages = {647-650},
      doi = {http://dx.doi.org/10.1109/WIIAT.2008.231}
    }
    
    Boella, G., Governatori, G., Hulstijn, J., Riveret, Ré., Rotolo, A. & van der Torre, L. Time and Defeasibility in FIPA ACL Semantics 2008 2008 IEEE/WIC/ACM International Conference on Web Intelligence and Intelligent Agent Technology, pp. 634-637  inproceedings DOI  
    Abstract: Inferences about communicative actions are often conditional, non-monotonic, and involve the issue of time. Most agent communication languages, however, ignore these issues, due to the difficulty to combine them in a single formalism. This paper addresses such issues in defeasible logic, and illustrates how to express a semantics for ACLs in order to make non-monotonic inferences on the basis of communicative actions.
    BibTeX:
    @inproceedings{wliamas08acl,
      author = {Boella, Guido and Governatori, Guido and Hulstijn, Joris and Riveret, Régis and Rotolo, Antonino and van der Torre, Leendert},
      title = {Time and Defeasibility in FIPA ACL Semantics},
      booktitle = {2008 IEEE/WIC/ACM International Conference on Web Intelligence and Intelligent Agent Technology},
      publisher = {IEEE Press},
      year = {2008},
      pages = {634-637},
      doi = {http://dx.doi.org/10.1109/WIIAT.2008.275}
    }
    
    Boella, G., Governatori, G., Hulstijn, J., Riveret, Régis., Rotolo, A. & van der Torre, L. FIPA Communicative Acts in Defeasible Logic 2007 Seventh IJCAI International Workshop on Nonmonotonic Reasoning, Action and Change (NRAC'07)  inproceedings  
    Abstract: In agent communication languages, the inferences that can be made on the basis of a communicative action are inherently conditional, and non-monotonic. For example, a proposal only leads to a commitment, on the condition that it is accepted. And in a persuasion dialogue, assertions may later be retracted. In this paper we therefore present a defeasible logic that can be used to express a semantics for agent communication languages, and to efficiently make inferences on the basis of communicative actions. The logic is non-monotonic, allows nested rules and mental attitudes as the content of communicative actions, and has an explicit way of expressing persistence over time. Moreover, it expresses that mental attitudes are publicly attributed to agents playing roles in the dialogue. To illustrate the usefulness of the logic, we reformalize the meta-theory underlying the FIPA semantics for agent communication, focusing on inform and propose. We show how composed speech acts can be formalized, and extend the semantics with an account of persuasion.
    BibTeX:
    @inproceedings{nrac:07:fipa,
      author = {Boella, Guido and Governatori, Guido and Hulstijn, Joris and Riveret, Régis and Rotolo, Antonino and van der Torre, Leemndert},
      title = {FIPA Communicative Acts in Defeasible Logic},
      booktitle = {Seventh IJCAI International Workshop on Nonmonotonic Reasoning, Action and Change (NRAC'07)},
      publisher = {IJCAI},
      year = {2007}
    }
    
    Boella, G., Governatori, G., Rotolo, A. & van der Torre, L. Lex minus dixit quam voluit, lex magis dixit quam voluit: A formal study on legal compliance and interpretation 2010
    Vol. 6237 AI Approaches to the Complexity of Legal Systems. Complex Systems, the Semantic Web, Ontologies, Argumentation, and Dialogue, pp. 162-183 
    inproceedings DOI  
    Abstract: This paper argues in favour of the necessity of dynamically restricting and expanding the applicability of norms regulating computer systems like multiagent systems, in situations where the compliance to the norm does not achieve the purpose of the norm. We propose a logical framework which distinguishes between constitutive and regulative norms and captures the norm change power and at the same time the limitations of the judicial system in dynamically revising the set of constitutive rules defining the concepts on which the applicability of norms is based. In particular, the framework is used to reconstruct some interpretive arguments described in legal theory such as those corresponding to the Roman maxims lex minus dixit quam voluit and lex magis dixit quam voluit. The logical framework is based on an extension of defeasible logic.
    BibTeX:
    @inproceedings{aicol2009,
      author = {Boella, Guido and Governatori, Guido and Rotolo, Antonino and van der Torre, Leendert},
      title = {Lex minus dixit quam voluit, lex magis dixit quam voluit: A formal study on legal compliance and interpretation},
      booktitle = {AI Approaches to the Complexity of Legal Systems. Complex Systems, the Semantic Web, Ontologies, Argumentation, and Dialogue},
      publisher = {Springer},
      year = {2010},
      volume = {6237},
      pages = {162-183},
      doi = {http://dx.doi.org/10.1007/978-3-642-16524-5_11}
    }
    
    Boella, G., Governatori, G., Rotolo, A. & van der Torre, L. A Logical Understanding of Legal Interpretation 2010 Principles of Knowledge Representation and Reasoning: Proceedings of the Twelfth International Conference, KR 2010  inproceedings URL  
    Abstract: If compliance with a norm does not achieve its purpose, then its applicability must dynamically be restricted or expanded. Legal interpretation is a mechanism from law allowing norms to be adapted to unforeseen situations. We model this mechanism for norms regulating computer systems by representing the purpose of norms by social goals and by revising the constitutive rules defining the applicability of norms. We illustrate the interpretation mechanism by examples.
    BibTeX:
    @inproceedings{kr2010,
      author = {Boella, Guido and Governatori, Guido and Rotolo, Antonino and van der Torre, Leendert},
      title = {A Logical Understanding of Legal Interpretation},
      booktitle = {Principles of Knowledge Representation and Reasoning: Proceedings of the Twelfth International Conference, KR 2010},
      publisher = {AAAI Press},
      year = {2010},
      url = {http://aaai.org/ocs/index.php/KR/KR2010/paper/view/1379}
    }
    
    Boella, G., Governatori, G., Rotolo, A. & van der Torre, L. A formal study on legal compliance and interpretation 2010 13 International Workshop on Non-Monotonic Reasoning (NMR 2010)  inproceedings  
    Abstract: This paper proposes a logical framework to capture the norm change power and the limitations of the judicial system in revising the set of constitutive rules defining the concepts on which the applicability of norms is based. In particular, we reconstruct the legal arguments leading to an extensive or restrictive interpretation of norms.
    BibTeX:
    @inproceedings{nmr10:lex,
      author = {Boella, Guido and Governatori, Guido and Rotolo, Antonino and van der Torre, Leendert},
      title = {A formal study on legal compliance and interpretation},
      booktitle = {13 International Workshop on Non-Monotonic Reasoning (NMR 2010)},
      publisher = {CEUR Workshop Proceedings},
      year = {2010}
    }
    
    Kamada, A., Governatori, G. & Sadiq, S. SBVR based Business Contract and Business Rule IDE 2010 (649) Proceedings of the RuleML-2010 Challenge, at the 4th International Web Rule Symposium, pp. 8.1-8.8  inproceedings  
    Abstract: We propose an IDE – Integrated Development Environment to model SBVR (Semantic of Business Vocabulary and Business Rule) compliant business rules [2] extracted from business contract of services and store them in an ontological structure of rules, facts and terms as defined in the SBVR metamodel. Business rules are based on principles of deontic logic for treating expressions in the form of normative policies. Deontic constraints express what parties to the contract are required to perform (obligations), what they are allowed to do (permissions), or what they are not allowed to do (prohibitions).
    BibTeX:
    @inproceedings{ruleml10challenge,
      author = {Kamada, Aqueo and Governatori, Guido and Sadiq, Shazia},
      title = {SBVR based Business Contract and Business Rule IDE},
      booktitle = {Proceedings of the RuleML-2010 Challenge, at the 4th International Web Rule Symposium},
      year = {2010},
      number = {649},
      pages = {8.1-8.8}
    }
    
    Chow, P. Y. & Governatori, G. Representing and Reasoning on XForms Document 2004 Database Technology 2004, pp. 141-150  inproceedings URL  
    Abstract: Forms are the most common way to interface users and Web-based applications. Traditional forms cannot provide the functionality needed to fulfil the requirements of complex applications. As such, there is a need for a more advanced format of forms to support Web-based application. We argued that XForms easily fit into this criterion of forms. In addition, we observed that there is a need for a tool to reason about the forms with respect to user needs and application requirements. We propose to use Description Logic ALCQI to reason about forms generated by XForms.
    BibTeX:
    @inproceedings{adc04cg,
      author = {Chow, Peng Yew and Governatori, Guido},
      title = {Representing and Reasoning on XForms Document},
      booktitle = {Database Technology 2004},
      publisher = {ACS},
      year = {2004},
      pages = {141-150},
      url = {http://crpit.com/confpapers/CRPITV27Cheow.pdf}
    }
    
    Dastani, M., Governatori, G., Rotolo, A., Song, I. & van der Torre, L. Contextual Deliberation of Cognitive Agents in Defeasible Logic 2007 6th International Conference on Autonomous Agents and Multi-Agent Systems, pp. 148-150  inproceedings  
    Abstract: This article extends Defeasible Logic to deal with the contextual deliberation process of cognitive agents. First, we introduce meta-rules to reason with rules. Meta-rules are rules that have as a consequent rules for motivational components, such as obligations, intentions and desires. In other words, they include nested rules. Second, we introduce explicit preferences among rules. They deal with complex structures where nested rules can be involved.
    BibTeX:
    @inproceedings{aamas07,
      author = {Dastani, Mehdi and Governatori, Guido and Rotolo, Antonino and Song, Insu and van der Torre, Leendert},
      title = {Contextual Deliberation of Cognitive Agents in Defeasible Logic},
      booktitle = {6th International Conference on Autonomous Agents and Multi-Agent Systems},
      publisher = {ACM},
      year = {2007},
      pages = {148-150}
    }
    
    Dastani, M., Governatori, G., Rotolo, A., Song, I. & van der Torre, L. Contextual Agent Deliberation in Defeasible Logic 2008 10 Pacific Rim International Workshop on Multi-Agents  inproceedings URL  
    Abstract: This article extends Defeasible Logic to deal with the contextual deliberation process of cognitive agents. First, we introduce meta-rules to reason with rules. Meta-rules are rules that have as a consequent rules for motivational components, such as obligations, intentions and desires. In other words, they include nested rules. Second, we introduce explicit preferences among rules. They deal with complex structures where nested rules can be involved.
    BibTeX:
    @inproceedings{prima07:contextual,
      author = {Dastani, Mehdi and Governatori, Guido and Rotolo, Antonino and Song, Insu and van der Torre, Leendert},
      title = {Contextual Agent Deliberation in Defeasible Logic},
      booktitle = {10 Pacific Rim International Workshop on Multi-Agents},
      publisher = {Springer},
      year = {2008},
      url = {http://www.springerlink.com}
    }
    
    Dastani, M., Governatori, G., Rotolo, A. & van der Torre, L. Programming Cognitive Agents in Defeasible Logic 2005 Logic for Programming, Artificial Intelligence, and Reasoning, 12th International Conference, pp. 621-636  inproceedings DOI  
    Abstract: Defeasible Logic is extended to programming languages for cognitive agents with preferences and actions for planning. We define rule-based agent theories that contain preferences and actions, together with inference procedures. We discuss patterns of agent types in this setting. Finally, we illustrate the language by an example of an agent reasoning about web-services.
    BibTeX:
    @inproceedings{lpar05,
      author = {Dastani, Mehdi and Governatori, Guido and Rotolo, Antonino and van der Torre, Leendert},
      title = {Programming Cognitive Agents in Defeasible Logic},
      booktitle = {Logic for Programming, Artificial Intelligence, and Reasoning, 12th International Conference},
      publisher = {Springer},
      year = {2005},
      pages = {621-636},
      doi = {http://dx.doi.org/10.1007/11591191_43}
    }
    
    Dastani, M., Governatori, G., Rotolo, A. & van der Torre, L. Preferences of Agents in Defeasible Logic 2005 AI 2005: Advances in Artificial Intelligence, 18th Australian Joint Conference on Artificial Intelligence, pp. 695-704  inproceedings DOI  
    Abstract: We are interested in programming languages for cognitive agents with preferences. We define rule-based agent theories and inference procedures in defeasible logic, and in this setting we discuss patterns of agent behavior called agent types.
    BibTeX:
    @inproceedings{ai05,
      author = {Dastani, Mehdi and Governatori, Guido and Rotolo, Antonino and van der Torre, Leendert},
      title = {Preferences of Agents in Defeasible Logic},
      booktitle = {AI 2005: Advances in Artificial Intelligence, 18th Australian Joint Conference on Artificial Intelligence},
      publisher = {Springer},
      year = {2005},
      pages = {695-704},
      doi = {http://dx.doi.org/10.1007/11589990_72}
    }
    
    Di Giusto, P. & Governatori, G. A New Approach to Base Revision 1999 (1695) Progress in Artificial Intelligence, pp. 327-341  inproceedings URL  
    Abstract: We present three approaches to revision of belief bases, which are also examined in the case in which the sentences in the base are partitioned between those which can and those which cannot be changed; the approaches are shown to be semantically equivalent. A new approach is then presented, based on the modification of individual rules, instead of deletion. The resulting base is semantically equivalent to that generated by the other approaches, in the sense that it has the same models, but the rule part alone has fewer models, that is, is subjected to a smaller change.
    BibTeX:
    @inproceedings{epia1,
      author = {Di Giusto, Paolo and Governatori, Guido},
      title = {A New Approach to Base Revision},
      booktitle = {Progress in Artificial Intelligence},
      publisher = {Springer-Verlag},
      year = {1999},
      number = {1695},
      pages = {327-341},
      url = {http://springerlink.metapress.com/index/FEM2H5B5FXWN3QNM}
    }
    
    Di Giusto, P. & Governatori, G. Analytic modal revision for multi-agent systems 1999 (1695) Progress in Artificial Intelligence, pp. 282-296  inproceedings URL  
    Abstract: We present two models of hierarchical structured multi-agents, and we describe how to obtain a modal knowledge base from distributed sources. We then propose a computationally oriented revision procedure for modal knowledge bases. This procedure is based on a labelled tableaux calculi supplemented with a formalism to record the dependencies of the formulae. The dependencies are then used to reconstruct the minimal inconsistent sets, and the sub-formulae responsible for the inconsistencies are revised according to well-defined chains of modal functions.
    BibTeX:
    @inproceedings{epia2,
      author = {Di Giusto, Paolo and Governatori, Guido},
      title = {Analytic modal revision for multi-agent systems},
      booktitle = {Progress in Artificial Intelligence},
      publisher = {Springer-Verlag},
      year = {1999},
      number = {1695},
      pages = {282-296},
      url = {http://springerlink.metapress.com/index/Y9FQD8JXTTN7N9YG}
    }
    
    Di Giusto, P. & Governatori, G. Modifying Is Better Than Deleting: A New Approach To Base Revision 1999 AI*IA 99, pp. 145-154  inproceedings  
    Abstract: We present three approaches to belief base revision, which are examined also in the case in which the sentences in the base are partitioned between those which can and those which cannot be changed; the approaches are shown to be semantically equivalent. A new approach is then presented, based on the modification of individual rules, instead of deletion. The resulting base is semantically equivalent to that generated by the other approaches, in the sense that it has the same models, but the rule part alone has less models, that is, is subjected to a smaller change.
    BibTeX:
    @inproceedings{revision-ai*ia,
      author = {Di Giusto, Paolo and Governatori, Guido},
      title = {Modifying Is Better Than Deleting: A New Approach To Base Revision},
      booktitle = {AI*IA 99},
      publisher = {Pitagora},
      year = {1999},
      pages = {145-154}
    }
    
    Dumas, M., Aldred, L., Governatori, G. & ter Hofstede, A. H. Probabilistic Automated Bidding in Multiple Auctions 2005 Journal of Electronic Commerce Research
    Vol. 5 (1) , pp. 23-47 
    article DOI  
    Abstract: This paper presents an approach to develop bidding agents that participate in multiple alternative auctions, with the goal of obtaining an item with a given probability. The approach consists of a prediction method and a planning algorithm. The prediction method exploits the history of past auctions in order to build probability functions capturing the belief that a bid of a given price may win a given auction. The planning algorithm computes a price, such that by sequentially bidding in a subset of the relevant auctions, the agent can obtain the item at that price with the desired probability. The approach addresses the case where the auctions are for substitutive items with different values. Experimental results show that the approach increases the payoff of their users and the welfare of the market.
    BibTeX:
    @article{jecr,
      author = {Dumas, Marlon and Aldred, Lachlan and Governatori, Guido and ter Hofstede, Arthur H.M.},
      title = {Probabilistic Automated Bidding in Multiple Auctions},
      journal = {Journal of Electronic Commerce Research},
      publisher = {Springer Science+Business Media B.V.,},
      year = {2005},
      volume = {5},
      number = {1},
      pages = {23-47},
      doi = {http://dx.doi.org/10.1023/B:ELEC.0000045972.75533.90}
    }
    
    Dumas, M., Aldred, L., Governatori, G., ter Hofstede, A. H. & Russell, N. A Probabilistic Approach to Automated Bidding in Alternative Auctions 2002 WWW2002, pp. 99-108  inproceedings DOI  
    Abstract: This paper presents an approach to develop bidding agents that participate in multiple alternative auctions, with the goal of obtaining an item at the lowest price. The approach consists of a prediction method and a planning algorithm. The prediction method exploits the history of past auctions in order to build probability functions capturing the belief that a bid of a given price may win a given auction. The planning algorithm computes the lowest price, such that by sequentially bidding in a subset of the relevant auctions, the agent can obtain the item at that price with an acceptable probability. The approach addresses the case where the auctions are for substitutable items with different values. Experimental results are reported, showing that the approach increases the payoff of their users and the welfare of the market
    BibTeX:
    @inproceedings{www,
      author = {Dumas, Marlon and Aldred, Lachlan and Governatori, Guido and ter Hofstede, Arthur H.M. and Russell, Nick},
      title = {A Probabilistic Approach to Automated Bidding in Alternative Auctions},
      booktitle = {WWW2002},
      publisher = {ACM Press},
      year = {2002},
      pages = {99-108},
      doi = {http://dx.doi.org/10.1145/511446.511460}
    }
    
    Dumas, M., Governatori, G., ter Hofstede, A. H. & Russell, N. An Architecture for Assembling Agents that Participate in Alternative Heterogeneous Auctions 2002 RIDE-2EC 2002, pp. 75-83  inproceedings DOI  
    Abstract: This paper addresses the issue of developing agents capable of participating in several potentially simultaneous auctions of different kinds (English, First-Price, Vickrey), with the goal of finding the best price for an item on behalf of their users. Specifically, a multi-agent architecture is proposed, in which a manager agent cooperates with several expert agents, each specialised in a specific kind of auction. The expert agents communicate their knowledge to the manager agent in the form of probability functions, capturing the likelihood that a bid of a given price may win an auction. Given a set of such functions, the manager agent builds a bidding plan that it executes in concert with the expert agents.
    BibTeX:
    @inproceedings{ride,
      author = {Dumas, Marlon and Governatori, Guido and ter Hofstede, Arthur H.M. and Russell, Nick},
      title = {An Architecture for Assembling Agents that Participate in Alternative Heterogeneous Auctions},
      booktitle = {RIDE-2EC 2002},
      publisher = {IEEE Press},
      year = {2002},
      pages = {75-83},
      doi = {http://dx.doi.org/10.1109/RIDE.2002.995101}
    }
    
    Dumas, M., Governatori, G., ter Hofstede, A. H. M. & Oaks, P. A Formal Approach to Negotiating Agents Development 2002 Electronic Commerce Research and Applications
    Vol. 1 (2) , pp. 193-207 
    article URL  
    Abstract: This paper presents a formal and executable approach to capture the behaviour of parties involved in a negotiation. A party is modeled as a negotiating agent composed of a communication module, a control module, a reasoning module, and a knowledge base. The control module is expressed as a statechart, and the reasoning module as a defeasible logic program. A strategy specification therefore consists of a statechart, a set of defeasible rules, and a set of initial facts. Such a specification can be dynamically plugged into an agent shell incorporating a statechart interpreter and a defeasible logic inference engine, in order to yield an agent capable of participating in a given type of negotiations. The choice of statecharts and defeasible logic with respect to other formalisms is justified against a set of desirable criteria, and their suitability is illustrated through concrete examples of bidding and multi-lateral bargaining scenarios.
    BibTeX:
    @article{ecra2002,
      author = {Dumas, Marlon and Governatori, Guido and ter Hofstede, Arthur H. M. and Oaks, Phillipa },
      title = {A Formal Approach to Negotiating Agents Development},
      journal = {Electronic Commerce Research and Applications},
      year = {2002},
      volume = {1},
      number = {2},
      pages = {193-207},
      url = {http://www.elsevier.com/locate/ecra}
    }
    
    Eriksson Lundström, J., Governatori, G., Thakur, S. & Padmanabhan, V. An Asymmetric Protocol for Argumentation Games in Defeasible Logic 2008 10 Pacific Rim International Workshop on Multi-Agents  inproceedings DOI  
    Abstract: Agent interactions where the agents hold conflicting goals could be modelled as adversarial argumentation games. In many real-life situations (e.g., criminal litigation, consumer legislation), due to ethical, moral or other principles governing interaction, the burden of proof, i.e., which party is to lose if the evidence is balanced te4, is a priori fixed to one of the parties. Analogously, when resolving disputes in a heterogeneous agent-system the unequal importance of different agents for carrying out the overall system goal need to be accounted for. In this paper we present an asymmetric protocol for an adversarial argumentation game in Defeasible Logic, suggesting Defeasible Logic as a general representation formalism for argumentation games modelling agent interactions.
    BibTeX:
    @inproceedings{prima07:dialogue,
      author = {Eriksson Lundström, Jenny and Governatori, Guido and Thakur, Subhasis and Padmanabhan, Vineet},
      title = {An Asymmetric Protocol for Argumentation Games in Defeasible Logic},
      booktitle = {10 Pacific Rim International Workshop on Multi-Agents},
      publisher = {Springer},
      year = {2008},
      doi = {?}
    }
    
    Gabbay, D. M. & Governatori, G. Fibred Modal Tableaux 2000 Labelled Deduction, pp. 163-194  incollection  
    Abstract: We describe a general and uniform tableau methodology for multi-modal logics arising from Gabbay's methodology of fibring and Governatori's labelled tableau system
    BibTeX:
    @incollection{fmt,
      author = {Dov M. Gabbay and Governatori, Guido},
      title = {Fibred Modal Tableaux},
      booktitle = {Labelled Deduction},
      publisher = {Kluwer},
      year = {2000},
      pages = {163-194}
    }
    
    Gabbay, D. M. & Governatori, G. Dealing with Label Dependent Deontic Modalities 1998 Norms, Logics and Information Systems. New Studies in Deontic Logic, pp. 311-330  incollection  
    Abstract: In this paper, following Scott's advice, we argue that normative reasoning can be represented in a multi-setting framework; in particular in a multi-modal one, where modalities are indexed. Indexed modalities can model several aspects involved in normative reasoning. Systems are combined using Gabbay's fibring methodology which provides complete semantics that can be used to model a labelled tableau-like proofs system.
    BibTeX:
    @incollection{deon98,
      author = {Dov M. Gabbay and Governatori, Guido},
      title = {Dealing with Label Dependent Deontic Modalities},
      booktitle = {Norms, Logics and Information Systems. New Studies in Deontic Logic},
      publisher = {IOS Press},
      year = {1998},
      pages = {311-330}
    }
    
    Gabbay, D. M. & Governatori, G. Fibred Modal Tableaux (Preliminary Report) 1998 Tableaux'98: Position Papers, pp. 33-48  inproceedings  
    Abstract: We describe a general and uniform tableau methodology for multi-modal logics arising from Gabbay's methodology of fibring and Governatori's labelled tableau system
    BibTeX:
    @inproceedings{fmt-old,
      author = {Dov M. Gabbay and Governatori, Guido},
      title = {Fibred Modal Tableaux (Preliminary Report)},
      booktitle = {Tableaux'98: Position Papers},
      year = {1998},
      pages = {33-48}
    }
    
    Gelati, J., Governatori, G., Rotolo, A. & Sartor, G. Declarative Power, Representation, and Mandate: A Formal Anaysis 2002 Legal Knowledge and Information Systems, pp. 41-52  incollection URL  
    Abstract: In this paper we provide a formal framework for developing the idea of normative co-ordination. We argue that this idea is based on the assumption that agents can achieve flexible co-ordination by conferring normative positions to other agents. These positions include duties, permissions, and powers. In particular, we introduce the idea of declarative power, which consists in the capacity of the power-holder of creating normative positions, involving other agents, simply by ``proclaiming'' such positions. In addition, we account also for the concepts of representation, consisting in the representative's capacity of acting in the name of his principal, and of mandate, which corresponds the mandatee's duty to act as the mandator has requested. Finally, we show how the above framework can be applied to the contract-net protocol.
    BibTeX:
    @incollection{jurix02,
      author = {Gelati, Jonathan and Governatori, Guido and Rotolo, Antonino and Sartor, Giovanni},
      title = {Declarative Power, Representation, and Mandate: A Formal Anaysis},
      booktitle = {Legal Knowledge and Information Systems},
      publisher = {IOS Press},
      year = {2002},
      pages = {41-52},
      url = {http://www.jurix.nl/pdf/j02-05.pdf}
    }
    
    Gelati, J., Governatori, G., Rotolo, A. & Sartor, G. Normative Autonomy and Normative Co-ordination: Declarative Power, Representation, and Mandate 2004 Artificial Intelligence and Law
    Vol. 12 (1-2) , pp. 53-81 
    article DOI  
    Abstract: In this paper we provide a formal analysis of the idea of normative co-ordination. We argue that this idea is based on the assumption that agents can achieve flexible co-ordination by conferring normative positions to other agents. These positions include duties, permissions, and powers. In particular, we explain the idea of declarative power, which consists in the capacity of the power-holder of creating normative positions, involving other agents, simply by ``proclaiming'' such positions. In addition, we account also for the concepts of representation, namely the representative's capacity of acting in the name of his principal, and of mandate, which is the mandatee's duty to act as the mandator has requested. Finally, we show how the framework can be applied to represent the contract-net protocol. Some brief remarks on future research and applications conclude this contribution.
    BibTeX:
    @article{GelGovRotSar:AIL:04:Normative,
      author = {Gelati, Jonathan and Governatori, Guido and Rotolo, Antonino and Sartor, Giovanni},
      title = {Normative Autonomy and Normative Co-ordination: Declarative Power, Representation, and Mandate},
      journal = {Artificial Intelligence and Law},
      year = {2004},
      volume = {12},
      number = {1-2},
      pages = {53-81},
      doi = {http://dx.doi.org/10.1007/s10506-004-2807-0}
    }
    
    Gordon, T. F., Governatori, G. & Rotolo, A. Rules and Norms: Requirements for Rule Interchange Languages in the Legal Domain 2009 (5858) Rule Representation, Interchange and Reasoning on the Web, pp. 282-296  inproceedings DOI  
    Abstract: In this survey paper we summarize the requirements for rule interchange languages for applications in the legal domain and use these requirements to evaluate RuleML, SBVR, SWRL and RIF. We also present the Legal Knowledge Interchange Format (LKIF), a new rule interchange format developed specifically for applications in the legal domain.
    BibTeX:
    @inproceedings{ruleml09:rules_and_norms,
      author = {Gordon, Thomas F. and Governatori, Guido and Rotolo, Antonino},
      title = {Rules and Norms: Requirements for Rule Interchange Languages in the Legal Domain},
      booktitle = {Rule Representation, Interchange and Reasoning on the Web},
      publisher = {Springer},
      year = {2009},
      number = {5858},
      pages = {282-296},
      doi = {http://dx.doi.org/10.1007/978-3-642-04985-9_26}
    }
    
    Governatori, G. Defeasible Description Logic 2004 Rules and Rule Markup Languages for the Semantic Web: Third International Workshop, RuleML 2004, pp. 98-112  inproceedings DOI  
    Abstract: We propose to extend description logic with defeasible rules, and to use the inferential mechanism of defeasible logic to reason with description logic constructors.
    BibTeX:
    @inproceedings{ruleml04,
      author = {Governatori, Guido},
      title = {Defeasible Description Logic},
      booktitle = {Rules and Rule Markup Languages for the Semantic Web: Third International Workshop, RuleML 2004},
      publisher = {Springer-Verlag},
      year = {2004},
      pages = {98-112},
      doi = {http://dx.doi.org/10.1007/b102922}
    }
    
    Governatori, G. Labelled Modal Tableaux 2008
    Vol. 7 Advances in Modal Logic, pp. 87-110 
    incollection URL  
    Abstract: Labelled tableaux are extensions of semantic tableaux with annotations (labels, indices) whose main function is to enrich the modal object language with semantic elements. This paper consists of three parts. In the first part we consider some options for labels: simple constant labels vs labels with free variables, logic depended inference rules vs labels manipulation based on a label algebra. In the second and third part we concentrate on a particular labelled tableaux system called KEM using free variable and a specialised label algebra. Specifically in the second part we show how labelled tableaux (KEM) can account for different types of logics (e.g., non-normal modal logics and conditional logics). In the third and final part we investigate the relative complexity of labelled tableaux systems and we show that the uses of KEM's label algebra can lead to speed up on proofs.
    BibTeX:
    @incollection{aiml08,
      author = {Governatori, Guido},
      title = {Labelled Modal Tableaux},
      booktitle = {Advances in Modal Logic},
      publisher = {College Publications},
      year = {2008},
      volume = {7},
      pages = {87-110},
      url = {http://www.aiml.net/volumes/volume7/Governatori.pdf}
    }
    
    Governatori, G. Ideality and Subideality from a Computational Point of View 1998
    Vol. Part II From Practical Reason to Legal Computer Science. Legal Computer Science, pp. 315-329 
    incollection  
    BibTeX:
    @incollection{ivr,
      author = {Governatori, Guido},
      title = {Ideality and Subideality from a Computational Point of View},
      booktitle = {From Practical Reason to Legal Computer Science. Legal Computer Science},
      publisher = {Clueb},
      year = {1998},
      volume = {Part II},
      pages = {315-329}
    }
    
    Governatori, G. Labelled Tableaux for Multi-Modal Logics 1995 Theorem Proving with Analytic Tableaux and Related Methods, pp. 79-94  inproceedings  
    Abstract: In this paper we present a tableau-like proof system for multi-modal logics based on D'Agostino and Mondadori's classical refutation system $KE$. The proposed system, that we call $KEM$, works for the logics $S5A$ and $S5P_(n)$ which have been devised by Mayer and van der Hoek for formalizing the notions of actuality and preference. We shall also show how $KEM$ works with the normal modal logics $K45, D45$, and $S5$ which are frequently used as bases for epistemic operators -- knowledge, belief, and we shall briefly sketch how to combine knowledge and belief in a multi-agent setting through $KEM$ modularity.
    BibTeX:
    @inproceedings{tableau,
      author = {Governatori, Guido},
      title = {Labelled Tableaux for Multi-Modal Logics},
      booktitle = {Theorem Proving with Analytic Tableaux and Related Methods},
      publisher = {Springer-Verlag},
      year = {1995},
      pages = {79-94}
    }
    
    Governatori, G. KE+: Beyond Refutation 1995 KI-95 Activities: Workshops, Posters, Demos, pp. 75-76  inproceedings  
    Abstract: The system KE+, a tableau-like proof system based on D'Agostino-Mondadori KE, is presented in this paper. This system avoids some of the drawbacks of other proof methods. In fact it is completly analytical, it is able to detect whether a formula is either a tautology or a contradiction or only a satisfiable one; in the course of a proof it can detect whether a subformula is a tautology and it uses this fact in the proof of the main formula
    BibTeX:
    @inproceedings{ke+,
      author = {Governatori, Guido},
      title = {KE+: Beyond Refutation},
      booktitle = {KI-95 Activities: Workshops, Posters, Demos},
      year = {1995},
      pages = {75-76}
    }
    
    Governatori, G. Labelling Ideality and Subideality 1996 (1085) Practical Reasoning, pp. 291-304  inproceedings  
    Abstract: In this paper we suggest ways in which logic and law may usefully relate; and we present an analytic proof system dealing with the Jones Pörn's deontic logic of Ideality and Subideality, which offers some suggestions about how to embed legal systems in label formalism.
    BibTeX:
    @inproceedings{fapr,
      author = {Governatori, Guido},
      title = {Labelling Ideality and Subideality},
      booktitle = {Practical Reasoning},
      publisher = {Springer-Verlag},
      year = {1996},
      number = {1085},
      pages = {291-304}
    }
    
    Governatori, G. On the Relative Complexity of Modal Tableaux 2003
    Vol. 78 CATS'03, pp. 36-53 
    inproceedings URL  
    Abstract: We investigate the relative complexity of two free-variable labelled modal tableaux (KEM and Single Step Tableaux, . We discuss the reasons why p-simulation is not a proper measure of the relative complexity of tableaux-like proof systems, and we propose an improved comparison scale (p-search-simulation). Finally we show that KEM p-search-simulates SST while SST cannot p-search-simulate
    BibTeX:
    @inproceedings{cats03,
      author = {Governatori, Guido},
      title = {On the Relative Complexity of Modal Tableaux},
      booktitle = {CATS'03},
      publisher = {Elsevier},
      year = {2003},
      volume = {78},
      pages = {36-53},
      url = {http://www.elsevier.nl/locate/entcs/volume78.html}
    }
    
    Governatori, G. A Duplication and Loop Checking Free System for S4 1996 (Technical Report 154-96) 5$^th$ Workshop on Theorem Proving with Analytic Tableaux and Related Methods (Short Papers), pp. 19-32  inproceedings  
    Abstract: Most of the sequent/tableau based proof systems for the modal logic S4 need to duplicate formulas and thus are required to adopt some method of loop checking. In what follows we present a tableau-like proof system for S4, based on D'Agostino and Mondadori's classical KE, which is free of duplication and loop checking. The key feature of this system (let us call it KES4) consists in its use of (i) a label formalism which models the semantics of the modal operators according to the usual conditions for S4; and (ii) a label unification scheme which tells us when two labels ``denote'' the same world in the S4-model(s) generated in the course of proof search. Moreover, it uses special closure conditions to check models for putative contradictions.
    BibTeX:
    @inproceedings{gov:tab96,
      author = {Governatori, Guido},
      title = {A Duplication and Loop Checking Free System for S4},
      booktitle = {5$^th$ Workshop on Theorem Proving with Analytic Tableaux and Related Methods (Short Papers)},
      publisher = {Università di Milano},
      year = {1996},
      number = {Technical Report 154-96},
      pages = {19-32}
    }
    
    Governatori, G. A Logic Framework of Normative-based Contract Management 2010 Fourth International Workshop on Juris-informatics (JURISIN 2010)  inproceedings  
    Abstract: In this paper an extended Defeasible Logic framework is presented to do the representation and reasoning work for the normative-based contract management. A simple case based on FIDIC is followed as the usage example. This paper is based on the idea that normative concepts and normative rules should play the decisive roles in the normative-based contract management. Those normative concepts and rules are based on the normative literals and operators like action, obligation, permission and violation. The normative reduction is based on the normative concepts, normative connections and normative rules, especially on the superiority relation over the defeasible rules.
    BibTeX:
    @inproceedings{jurisin10contract,
      author = {Governatori, Guido},
      title = {A Logic Framework of Normative-based Contract Management},
      booktitle = {Fourth International Workshop on Juris-informatics (JURISIN 2010)},
      year = {2010}
    }
    
    Governatori, G. Law, Logic and Business Processes 2010 Third International Workshop on Requirements Engineering and Law  inproceedings  
    Abstract: Since its inception one of the aims of legal informatics has been to provide tools to support and improve the day to day activities of legal and normative practice and a better understanding of legal reasoning. The internet revolutions, where more and more daily activities are routinely performed with the support of ITC tools, offers new opportunities to legal informatics. We argue that the current technology begins to be mature enough to embrace in the challenge to make intelligent ICT support widespread in the legal and normative domain. In this paper we examine a logical model to encode norms and we use the formalisation of relevant law and regulations for regulatory compliance for business processes.
    BibTeX:
    @inproceedings{relaw2010,
      author = {Governatori, Guido},
      title = {Law, Logic and Business Processes},
      booktitle = {Third International Workshop on Requirements Engineering and Law},
      publisher = {IEEE},
      year = {2010}
    }
    
    Governatori, G. Representing Business Contracts in RuleML 2005 International Journal of Cooperative Information Systems
    Vol. 14 (2-3) , pp. 181-216 
    article DOI  
    Abstract: This paper presents an approach for the specification and implementation of translating contracts from a human-oriented form into an executable representation for monitoring. This will be done in the setting of The task of monitoring contract execution and performance requires a logical account of deontic and defeasible aspects of legal language; currently such aspects are not covered by accordingly we show how to extend it to cover such notions. From its logical form, the contract will be thus transformed into a machine readable rule notation and eventually implemented as executable semantics via any mark-up languages depending on the client's preference, for contract monitoring purposes.
    BibTeX:
    @article{coala,
      author = {Governatori, Guido},
      title = {Representing Business Contracts in RuleML},
      journal = {International Journal of Cooperative Information Systems},
      year = {2005},
      volume = {14},
      number = {2-3},
      pages = {181-216},
      doi = {http://dx.doi.org/10.1142/S0218843005001092}
    }
    
    Governatori, G. Un modello formale per il ragionamento giuridico 1997 School: CIRFID, University of Bologna  phdthesis  
    BibTeX:
    @phdthesis{tesi,
      author = {Governatori, Guido},
      title = {Un modello formale per il ragionamento giuridico},
      school = {CIRFID, University of Bologna},
      year = {1997}
    }
    
    Governatori, G., Dumas, M., ter Hofstede, A. H. & Oaks, P. A formal approach to protocols and strategies for (legal) negotiation 2001 Procedings of the 8th International Conference on Artificial Intelligence and Law, pp. 168-177  inproceedings DOI  
    Abstract: We propose a formal and executable framework for expressing protocols and strategies for automated (legal) negotiation. In this framework a party involved in a negotiation is represented through a software agent composed of four modules: (i) a communication module which manages the interaction with the other agents; (ii) a control module; (iii) a reasoning module specified as a defeasible theory; and (iv) a knowledge base which bridges the control and the reasoning modules, while keeping track of past decisions and interactions. The choice of defeasible logic is justified against a set of desirable criteria for negotiation automation languages. Moreover, the suitability of the framework is illustrated through two case studies.
    BibTeX:
    @inproceedings{icail,
      author = {Governatori, Guido and Dumas, Marlon and Arthur H.M. ter Hofstede and Phillipa Oaks},
      title = {A formal approach to protocols and strategies for (legal) negotiation},
      booktitle = {Procedings of the 8th International Conference on Artificial Intelligence and Law},
      publisher = {ACM Press},
      year = {2001},
      pages = {168-177},
      doi = {http://dx.doi.org/10.1145/383535.383555}
    }
    
    Governatori, G., Gelati, J., Rotolo, A. & Sartor, G. Actions, Institutions, Powers. Preliminary Notes 2002 International Workshop on Regulated Agent-Based Social Systems: Theories and Applications (RASTA'02), pp. 131-147  inproceedings  
    Abstract: In this paper we analyse some logical notions relevant for representing the dynamics of institutionalised organisations. In particular, some well-known action concepts introduced in the Kanger-Lindahl-Pörn logical theory of agency are discussed and integrated. Secondly, moving from the work of Jones and Sergot, a logical characterisation is provided of the ideas of institutional links, ``counts-as'' connections, and institutional facts. This approach is then enriched by a new modal operator $proc$, intended to account for the autonomous and decentralised creation of new institutional facts and normative positions within institutions.
    BibTeX:
    @inproceedings{rasta02,
      author = {Governatori, Guido and Gelati, Jonathan and Rotolo, Antonino and Sartor, Giovanni},
      title = {Actions, Institutions, Powers. Preliminary Notes},
      booktitle = {International Workshop on Regulated Agent-Based Social Systems: Theories and Applications (RASTA'02)},
      publisher = {Fachbereich Informatik, Universität Hamburg},
      year = {2002},
      pages = {131-147}
    }
    
    Governatori, G. & Hoang, D. P. A Semantic Web Based Architecture for e-Contracts in Defeasible Logic 2005 Rules and Rule Markup Languages for the Semantic Web, First International Conference, RuleML 2005, , November 10-12, 2005, Proceedings, pp. 145-159  inproceedings DOI  
    Abstract: We introduce the DR-CONTRACT architecture to represent and reason on e-Contracts. The architecture extends the DR-device architecture by a deontic defeasible logic of violation. We motivate the choice for the logic and we show how to extend RuleML to capture the notions relevant to describe e-contracts for a monitoring perspective in Defeasible Logic.
    BibTeX:
    @inproceedings{ruleml05duy,
      author = {Governatori, Guido and Hoang, Duy Pham},
      title = {A Semantic Web Based Architecture for e-Contracts in Defeasible Logic},
      booktitle = {Rules and Rule Markup Languages for the Semantic Web, First International Conference, RuleML 2005, , November 10-12, 2005, Proceedings},
      publisher = {Springer},
      year = {2005},
      pages = {145-159},
      doi = {http://dx.doi.org/10.1007/11580072_12}
    }
    
    Governatori, G. & Hoang, D. P. DR-CONTRACT: An Architecture for e-Contracts in Defeasible Logic 2005 2nd EDOC Workshop on Contract Architectures and Languages (CoALA 2005)  inproceedings  
    Abstract: In this paper we present an architecture to represent and reason on e-Contracts based on the DR-device architecture supplemented with a deontic defeasible logic of violation. We motivate the choice for the logic and we show how to extend RuleML to capture the notions relevant to describe e-contracts for a monitoring perspective in Defeasible Logic.
    BibTeX:
    @inproceedings{coala05,
      author = {Governatori, Guido and Hoang, Duy Pham},
      title = {DR-CONTRACT: An Architecture for e-Contracts in Defeasible Logic},
      booktitle = {2nd EDOC Workshop on Contract Architectures and Languages (CoALA 2005)},
      publisher = {IEEE Digital Library},
      year = {2005},
      note = {Published on CD}
    }
    
    Governatori, G., Hoffmann, Jö., Sadiq, S. & Weber, I. Detecting Regulatory Compliance for Business Process Models through Semantic Annotations 2008 4th International Workshop on Business Process Design  inproceedings  
    Abstract: A given business process may face a large number of regulatory obligations the process may or comply with. Providing tools and techniques through which an evaluation of the compliance degree of a given process can be undertaken is seen as a key objective in emerging business process platforms. We address this problem through a diagnostic framework that provides the ability to assess the compliance gaps present in a given process. Checking whether a process is compliant with the rules involves enumerating all reachable states and is hence, in general, a hard search problem. The approach taken here allows to provide useful diagnostic information in polynomial time. The approach is based on two underlying techniques. A conceptually faithful representation for regulatory obligations is firstly provided by a formal rule language based on a non-monotonic deontic logic of violations. Secondly, processes are formalized through semantic annotations that allow a logical state space to be created. The intersection of the two allows us to devise an efficient method to detect compliance gaps; the method guarantees to detect all obligations that will necessarily arise during execution, but that will not necessarily be fulfilled.
    BibTeX:
    @inproceedings{bpd08,
      author = {Governatori, Guido and Hoffmann, Jörg and Sadiq, Shazia and Weber, Ingo},
      title = {Detecting Regulatory Compliance for Business Process Models through Semantic Annotations},
      booktitle = {4th International Workshop on Business Process Design},
      year = {2008}
    }
    
    Governatori, G., ter Hofstede, A. H. & Oaks, P. Is Defeasible Logic Applicable? 2001 Proceedings of the 2nd Australasian Workshop on Computational Logic, pp. 47-62  inproceedings  
    Abstract: In this paper the application of defeasible logic for automated negotiation is investigated. Defeasible logic is flexible enough to be adapted to several possible negotiation strategies, has efficient implementations, and provides a formal basis for analysis (e.g. to explain why a negotiation was not successful). Two case studies, one small and one more comprehensive, will be described and the feasibility of approaches based on defeasible logic will be discussed.
    BibTeX:
    @inproceedings{awcl-paper,
      author = {Governatori, Guido and Arthur H.M. ter Hofstede and Oaks, Phillipa},
      title = {Is Defeasible Logic Applicable?},
      booktitle = {Proceedings of the 2nd Australasian Workshop on Computational Logic},
      publisher = {Queensland University of Technology},
      year = {2001},
      pages = {47-62}
    }
    
    Governatori, G., ter Hofstede, A. H. & Oaks, P. Defeasible Logic for Automated Negotiation 2000 Proceedings of CollECTeR  inproceedings  
    Abstract: Negotiation plays a fundamental role in e-commerce. In this paper, the application of defeasible logic for automated negotiation is investigated. Defeasible logic is flexible enough to be adapted to several possible negotiation strategies, has efficient implementations, and provides a formal basis for analysis (e.g. to explain why a negotiation was not successful). Two case studies, one small and one more comprehensive, will be described and the feasibility of approaches based on defeasible logic will be discussed.
    BibTeX:
    @inproceedings{collecter,
      author = {Governatori, Guido and ter Hofstede, Arthur H.M. and Oaks, Phillipa},
      title = {Defeasible Logic for Automated Negotiation},
      booktitle = {Proceedings of CollECTeR},
      publisher = {Deakin University},
      year = {2000},
      note = {Published on CD}
    }
    
    Governatori, G., Hulstijn, J., Riveret, Ré. & Rotolo, A. On the Representation of Deadlines in a Rental Agreement 2007 Legal Knowledge and Information Systems, pp. 167-168  inproceedings  
    Abstract: The paper provides a conceptual analysis of deadlines, represented in Temporal Modal Defeasible Logic. The typology is based on the following parameters: kind of deontic operator, maintenance or achievement, presence of explicit sanctions, and persistence after the deadline. The adequacy of the typology is validated against a case study of a rental agreement.
    BibTeX:
    @inproceedings{jurix07,
      author = {Governatori, Guido and Hulstijn, Joris and Riveret, Régis and Rotolo, Antonino},
      title = {On the Representation of Deadlines in a Rental Agreement},
      booktitle = {Legal Knowledge and Information Systems},
      publisher = {IOS Press},
      year = {2007},
      pages = {167-168}
    }
    
    Governatori, G., Hulstijn, J., Riveret, Ré. & Rotolo, A. Characterising Deadlines in Temporal Modal Defeasible Logic 2007 20th Australian Joint Conference on Artificial Intelligence, AI 2007, pp. 486-496  inproceedings DOI  
    Abstract: We provide a conceptual analysis of several kinds of deadlines, represented in Temporal Modal Defeasible Logic. The paper presents a typology of deadlines, based on the following parameters: deontic operator, maintenance or achievement, presence or absence of sanctions, and persistence after the deadline. The deadline types are illustrated by a set of examples.
    BibTeX:
    @inproceedings{austai07:deadlines,
      author = {Governatori, Guido and Hulstijn, Joris and Riveret, Régis and Rotolo, Antonino},
      title = {Characterising Deadlines in Temporal Modal Defeasible Logic},
      booktitle = {20th Australian Joint Conference on Artificial Intelligence, AI 2007},
      publisher = {Springer},
      year = {2007},
      pages = {486-496},
      doi = {http://dx.doi.org/10.1007/978-3-540-76928-6_50}
    }
    
    Governatori, G. & Iannella, R. A Modelling and Reasoning Framework for Social Networks Policies 2010 Enterprise Information Systems   article  
    Abstract: Policy languages (such as privacy and rights) have had little impact on the wider community. Now that Social Networks have taken off, the need to revisit Policy languages and realign them towards Social Networks requirements has become more apparent. One such language is explored as to its applicability to the Social Networks masses. We also argue that policy languages alone are not sufficient and thus they should be paired with reasoning mechanisms to provide precise and unambiguous execution models of the policies. To this end we propose a computationally oriented model to represent, reason with and execute policies for Social Networks.
    BibTeX:
    @article{eis10networks,
      author = {Governatori, Guido and Iannella, Renato},
      title = {A Modelling and Reasoning Framework for Social Networks Policies},
      journal = {Enterprise Information Systems},
      year = {2010}
    }
    
    Governatori, G. & Iannella, R. Modelling and Reasoning Languages for Social Networks Policies 2009 Enterprise Distributed Object Computing Conference, 2009. EDOC '09. IEEE International, pp. 193-200  inproceedings DOI  
    Abstract: Policy languages (such as privacy and rights) have had little impact on the wider community. Now that Social Networks have taken off, the need to revisit Policy languages and realign them towards Social Networks requirements has become more apparent. One such language is explored as to its applicability to the Social Networks masses. We also argue that policy languages alone are not sufficient and thus they should be paired with reasoning mechanisms to provide precise and unambiguous execution models of the policies. To this end we propose a computationally oriented model to represent, reason with and execute policies for Social Networks.
    BibTeX:
    @inproceedings{edoc09,
      author = {Governatori, Guido and Iannella, Renato},
      title = {Modelling and Reasoning Languages for Social Networks Policies},
      booktitle = {Enterprise Distributed Object Computing Conference, 2009. EDOC '09. IEEE International},
      publisher = {IEEE},
      year = {2009},
      pages = {193-200},
      doi = {http://dx.doi.org/10.1109/EDOC.2009.19}
    }
    
    Governatori, G., Lomuscio, A. & Sergot, M. A Tableaux System for Deontic Interpreted Systems 2003 AI 2003: Advances in Artificial Intelligence, pp. 339-351  inproceedings URL  
    Abstract: We develop a labelled tableaux system for the modal logic $KD45^i-j_n$ extended with epistemic notions. This logic characterises a particular type of interpreted systems used to represent and reason about states of correct and incorrect functioning behaviour of the agents in a system, and of the system as a whole. The resulting tableaux system provides a simple decision procedure for the logic. We discuss these issues and we illustrate them with the help of simple examples
    BibTeX:
    @inproceedings{ai03gls,
      author = {Governatori, Guido and Lomuscio, Alessio and Sergot, Marek},
      title = {A Tableaux System for Deontic Interpreted Systems},
      booktitle = {AI 2003: Advances in Artificial Intelligence},
      publisher = {Springer-Verlag},
      year = {2003},
      pages = {339-351},
      url = {http://springerlink.metapress.com/index/T4TV93CGJ3VG18TK}
    }
    
    Governatori, G. & Luppi, A. Labelled tableaux for non-normal modal logics 2000 AI*IA 99: Advances in Artificial Intelligence, pp. 119-130  inproceedings URL  
    Abstract: In this paper we show how to extend a tableau-like proof system for normal modal logic, in order to deal with classes of non-normal modal logics, such as monotonic and regular, in a uniform and modular way.
    BibTeX:
    @inproceedings{nn,
      author = {Governatori, Guido and Luppi, Alessandro},
      title = {Labelled tableaux for non-normal modal logics},
      booktitle = {AI*IA 99: Advances in Artificial Intelligence},
      publisher = {Springer-Verlag},
      year = {2000},
      pages = {119-130},
      url = {http://springerlink.metapress.com/index/RJ5T3QVNRW3N4940}
    }
    
    Governatori, G. & Maher, M. J. An Argumentation-Theoretic Characterization of Defeasible Logic 2000 ECAI 2000. Proceedings of the 14th European Conference on Artificial Intelligence, pp. 469-474  inproceedings  
    Abstract: Defeasible logic is an efficient non-monotonic logic that is defined only proof-theoretically. It has potential application in some legal domains. We present here an argumentation semantics for defeasible logic that will be useful in these applications. Our development differs at several points from existing argumentation frameworks since there are several features of defeasible logic that have not been addressed in the literature.
    BibTeX:
    @inproceedings{ecai2000-2,
      author = {Governatori, Guido and Maher, Michael J.},
      title = {An Argumentation-Theoretic Characterization of Defeasible Logic},
      booktitle = {ECAI 2000. Proceedings of the 14th European Conference on Artificial Intelligence},
      publisher = {IOS Press},
      year = {2000},
      pages = {469-474}
    }
    
    Governatori, G., Maher, M. J., Antoniou, G. & Billington, D. Argumentation Semantics for Defeasible Logics 2000 PRICAI 2000: Topics in Artificial Intelligence, pp. 27-37  inproceedings URL  
    Abstract: Defeasible logic is an efficient non-monotonic logic that is defined only proof-theoretically. It has potential application in some legal domains. We present here argumentation semantics for variants of defeasible logic that will be useful in these applications.
    BibTeX:
    @inproceedings{pricai2000,
      author = {Governatori, Guido and Maher, Michael J. and Antoniou, Grigoris and Billington, David},
      title = {Argumentation Semantics for Defeasible Logics},
      booktitle = {PRICAI 2000: Topics in Artificial Intelligence},
      publisher = {Springer-Verlag},
      year = {2000},
      pages = {27-37},
      url = {http://www.springer.de/comp/lncs/index.html}
    }
    
    Governatori, G., Maher, M. J., Billington, D. & Antoniou, G. Argumentation Semantics for Defeasible Logics 2004 Journal of Logic and Computation
    Vol. 14 (5) , pp. 675-702 
    article DOI  
    Abstract: Defeasible reasoning is a simple but efficient rule-based approach to nonmonotonic reasoning. It has powerful implementations and shows promise to be applied in the areas of legal reasoning and the modeling of business rules. This paper establishes significant links between defeasible reasoning and argumentation. In particular, Dung-like argumentation semantics is provided for two key defeasible logics, of which one is ambiguity propagating and the other ambiguity blocking. There are several reasons for the significance of this work: (a) establishing links between formal systems leads to a better understanding and cross-fertilization, in particular our work sheds light on the argumentation-theoretic features of defeasible logic; (b) we provide the first ambiguity blocking Dung-like argumentation system; (c) defeasible reasoning may provide an efficient implementation platform for systems of argumentation; and (d) argumentation-based semantics support a deeper understanding of defeasible reasoning, especially in the context of the intended applications.
    BibTeX:
    @article{jlc:argumentation,
      author = {Governatori, Guido and Maher, Michael J. and Billington, David and Antoniou, Grigoris},
      title = {Argumentation Semantics for Defeasible Logics},
      journal = {Journal of Logic and Computation},
      year = {2004},
      volume = {14},
      number = {5},
      pages = {675-702},
      doi = {http://dx.doi.org/10.1093/logcom/14.5.675}
    }
    
    Governatori, G. & Milosevic, Z. An Approach for Validating BCL Contract Specifications 2005 2nd EDOC Workshop on Contract Architectures and Languages (CoALA 2005)  inproceedings  
    Abstract: We continue the study, started in [5], on the formal relationships between a domain specific contract language (BCL) and the logic of violation (FCL) proposed in [6,7]. We discuss the use of logical methods for the representation and analysis of business contracts. The proposed analysis is based on the notions of normal and canonical forms of contracts expressed in FCL. Finally we present a mapping from FCL to BCL that can be used to provide an executable model of a formal representation of a contract.
    BibTeX:
    @inproceedings{GovMil:Coala05:Approach,
      author = {Governatori, Guido and Milosevic, Zoran},
      title = {An Approach for Validating BCL Contract Specifications},
      booktitle = {2nd EDOC Workshop on Contract Architectures and Languages (CoALA 2005)},
      publisher = {IEEE Digital Library},
      year = {2005},
      note = {Published on CD}
    }
    
    Governatori, G. & Milosevic, Z. A Formal Analysis of a Business Contract Language 2006 International Journal of Cooperative Information Systems
    Vol. 15 (4) , pp. 659-685 
    article DOI  
    Abstract: This paper presents a formal system for reasoning about violations of obligations in contracts. The system is based on the formalism for the representation of contrary-to-duty obligations. These are the obligations that take place when other obligations are violated as typically applied to penalties in contracts. The paper shows how this formalism can be mapped onto the key policy concepts of a contract specification language, called Business Contract Language (BCL), previously developed to express contract conditions for run time contract monitoring. The aim of this mapping is to establish a formal underpinning for this key subset of BCL.
    BibTeX:
    @article{govmil:06:formal,
      author = {Governatori, Guido and Milosevic, Zoran},
      title = {A Formal Analysis of a Business Contract Language},
      journal = {International Journal of Cooperative Information Systems},
      year = {2006},
      volume = {15},
      number = {4},
      pages = {659-685},
      doi = {http://dx.doi.org/10.1142/S0218843006001529}
    }
    
    Governatori, G. & Milosevic, Z. Dealing with contract violations: formalism and domain specific language 2005 9th International Enterprise Distributed Object Computing Conference (EDOC 2005), pp. 46-57  inproceedings DOI  
    Abstract: This paper presents a formal system for reasoning about violations of obligations in contracts. The system is based on the formalism for the representation of contrary-to-duty obligations. These are the obligations that take place when other obligations are violated as typically applied to penalties in contracts. The paper shows how this formalism can be mapped onto the key policy concepts of a contract specification language. This language, called Business Contract Language (BCL) was previously developed to express contract conditions of relevance for run time contract monitoring. The aim of this mapping is to establish a formal underpinning for this key subset of BCL.
    BibTeX:
    @inproceedings{edoc2005,
      author = {Governatori, Guido and Milosevic, Zoran},
      title = {Dealing with contract violations: formalism and domain specific language},
      booktitle = {9th International Enterprise Distributed Object Computing Conference (EDOC 2005)},
      publisher = {IEEE Computer Society},
      year = {2005},
      pages = {46-57},
      doi = {http://dx.doi.org/10.1109/EDOC.2005.13}
    }
    
    Governatori, G., Milosevic, Z. & Sadiq, S. Compliance checking between business processes and business contracts 2006 10th International Enterprise Distributed Object Computing Conference (EDOC 2006), pp. 221-232  inproceedings DOI  
    Abstract: It is a typical scenario that many organisations have their business processes specified independently of their business contracts. This is because of the lack of guidelines and tools that facilitate derivation of processes from contracts but also because of the traditional mindset of treating contracts separately from business processes. This paper provides a solution to one specific problem that arises from this situation, namely the lack of mechanisms to check whether business processes are compliant with business contracts. The central part of the paper are logic based formalism for describing both the semantics of contract and the semantics of compliance checking procedures.
    BibTeX:
    @inproceedings{GovMilSad:edoc:06:compliance,
      author = {Governatori, Guido and Milosevic, Zoran and Sadiq, Shazia},
      title = {Compliance checking between business processes and business contracts},
      booktitle = {10th International Enterprise Distributed Object Computing Conference (EDOC 2006)},
      publisher = {IEEE Computing Society},
      year = {2006},
      pages = {221-232},
      doi = {http://dx.doi.org/10.1109/EDOC.2006.22}
    }
    
    Governatori, G., Olivieri, F., Scannapieco, S. & Cristani, M. Superiority Based Revision of Defeasible Theories 2010 (6403) RuleML 2010: 4th International Web Rule Symposium, pp. 104-118  inproceedings DOI  
    Abstract: We propose a systematic investigation on how to modify a preference relation in a defeasible logic theory to change the conclusions of the theory itself. We argue that the approach we adopt is applicable to legal reasoning, where users, in general, cannot change facts and rules, but can propose their preferences about the relative strength of the rules. We provide a comprehensive study of the possible combinatorial cases and we identify and analyse the cases where the revision process is successful.
    BibTeX:
    @inproceedings{ruleml10preferences,
      author = {Governatori, Guido and Olivieri, Francesco and Scannapieco, Simone and Cristani, Matteo},
      title = {Superiority Based Revision of Defeasible Theories},
      booktitle = {RuleML 2010: 4th International Web Rule Symposium},
      publisher = {Springer},
      year = {2010},
      number = {6403},
      pages = {104-118},
      doi = {http://dx.doi.org/10.1007/978-3-642-16289-3_10}
    }
    
    Governatori, G., Olivieri, F., Scannapieco, S. & Cristani, M. Superiority Based Revision of Defeasible Theories 2010 13 International Workshop on Non-Monotonic Reasoning (NMR 2010)  inproceedings  
    Abstract: We propose a systematic investigation on how to modify a preference relation in a defeasible logic theory to change the conclusions of the theory itself. We argue that the approach we adopt is applicable to legal reasoning, where users, in general, cannot change facts and rules, but can propose their preferences about the relative strength of the rules.

    We provide a comprehensive study of the possible combinatorial cases and we identify and analyse the cases where the revision process is successful.

    BibTeX:
    @inproceedings{nmr10:preferences,
      author = {Governatori, Guido and Olivieri, Francesco and Scannapieco, Simone and Cristani, Matteo},
      title = {Superiority Based Revision of Defeasible Theories},
      booktitle = {13 International Workshop on Non-Monotonic Reasoning (NMR 2010)},
      year = {2010}
    }
    
    Governatori, G., Orgun, M. A. & Liu, C. Modal tableaux for verifying stream authentication protocols 2009 Journal of Autonomous Agents and Multi Agent Systems
    Vol. 19 (1) , pp. 53-75 
    article DOI  
    Abstract: To develop theories to specify and reason about various aspects of multi-agent systems, many researchers have proposed the use of modal logics such as belief logics, logics of knowledge, and logics of norms. As multi-agent systems operate in dynamic environments, there is also a need to model the evolution of multi-agent systems through time. In order to introduce a temporal dimension to a belief logic, we combine it with a linear-time temporal logic using a powerful technique called fibring for combining logics. We describe a labelled modal tableaux system for the resulting fibred belief logic (FL) which can be used to automatically verify correctness of inter-agent stream authentication protocols. With the resulting fibred belief logic and its associated modal tableaux, one is able to build theories of trust for the description of, and reasoning about, multi-agent systems operating in dynamic environments.
    BibTeX:
    @article{jaamas:famas,
      author = {Governatori, Guido and Orgun, Mehmet A. and Liu, Chuchang},
      title = {Modal tableaux for verifying stream authentication protocols},
      journal = {Journal of Autonomous Agents and Multi Agent Systems},
      year = {2009},
      volume = {19},
      number = {1},
      pages = {53-75},
      doi = {http://dx.doi.org/10.1007/s10458-007-9027-4}
    }
    
    Governatori, G. & Padmanabhan, V. A Defeasible Logic of Policy-based Intention 2003 AI 2003: Advances in Artificial Intelligence, pp. 414-426  inproceedings URL  
    Abstract: Most of the theories on formalising intention interpret it as a unary modal operator in Kripkean semantics, which gives it a monotonic look. We argue that policy-based intentions tebratman1 exhibit non-monotonic behaviour which could be captured through a non-monotonic system like defeasible logic. To this end we outline a defeasible logic of intention. The proposed technique alleviates most of the problems related to logical omniscience. The proof theory given shows how our approach helps in the maintenance of intention-consistency in agent systems like BDI.
    BibTeX:
    @inproceedings{ai03v,
      author = {Governatori, Guido and Padmanabhan, Vineet},
      title = {A Defeasible Logic of Policy-based Intention},
      booktitle = {AI 2003: Advances in Artificial Intelligence},
      publisher = {Springer-Verlag},
      year = {2003},
      pages = {414-426},
      url = {http://springerlink.metapress.com/index/G9M5YK3UVDCY0JBB}
    }
    
    Governatori, G., Padmanabhan, V. & Rotolo, A. Rule-Based Agents in Temporalised Defeasible Logic 2006 Ninth Pacific Rim International Conference on Artificial Intelligence, pp. 31-40  inproceedings DOI  
    Abstract: This paper provides a framework based on temporal defeasible logic to reason about deliberative rule-based cognitive agents. Compared to previous works in this area our framework has the advantage that it can reason about temporal rules. We show that for rule-based cognitive agents deliberation is more than just deriving conclusions in terms of their mental components. Our paper is an extension of~teai05,lpar05 in the area of cognitive agent programming
    BibTeX:
    @inproceedings{pricai:06:dl,
      author = {Governatori, Guido and Padmanabhan, Vineet and Rotolo, Antonino},
      title = {Rule-Based Agents in Temporalised Defeasible Logic},
      booktitle = {Ninth Pacific Rim International Conference on Artificial Intelligence},
      publisher = {Springer},
      year = {2006},
      pages = {31-40},
      doi = {http://dx.doi.org/10.1007/11801603_6}
    }
    
    Governatori, G., Padmanabhan, V., Rotolo, A. & Sattar, A. A Defeasible Logic for Modelling Policy-based Intentions and Motivational Attitudes 2009 Logic Journal of the IGPL
    Vol. 17 (3) , pp. 227-265 
    article DOI  
    Abstract: In this paper we show how defeasible logic could formally account for the non-monotonic properties involved in motivational attitudes like intention and obligation. Usually, normal modal operators are used to represent such attitudes wherein classical logical consequence and the rule of necessitation comes into play i.e., $vdash A / vdash Box A$, that is from $vdash A$ derive $vdashBox A$. This means that such formalisms are affected by the Logical Omniscience problem. We show that policy-based intentions exhibit non-monotonic behaviour which could be captured through a non-monotonic system like defeasible logic. To this end we outline a defeasible logic of intention that specifies how modalities can be introduced and manipulated in a non-monotonic setting without giving rise to the problem of logical omniscience. In a similar way we show how to add deontic modalities defeasibly and how to integrate them with other motivational attitudes like beliefs and goals. Finally we show that the basic aspect of the BOID architecture is captured by this extended framework.
    BibTeX:
    @article{igpl09policy,
      author = {Governatori, Guido and Padmanabhan, Vineet and Rotolo, Antonino and Sattar, Abdul},
      title = {A Defeasible Logic for Modelling Policy-based Intentions and Motivational Attitudes},
      journal = {Logic Journal of the IGPL},
      year = {2009},
      volume = {17},
      number = {3},
      pages = {227-265},
      doi = {http://dx.doi.org/10.1093/jigpal/jzp006}
    }
    
    Governatori, G., Padmanabhan, V. N. & Sattar, A. On Fibring Semantics for BDI Logics 2002 Jelia 2002, pp. 198-210  inproceedings URL  
    Abstract: This study examines BDI logics in the context of Gabbay's fibring semantics. We show that dovetailing (a special form of fibring) can be adopted as a semantic methodology to combine BDI logics. We develop a set of interaction axioms that can capture static as well as dynamic aspects of the mental states in BDI systems, using Catach's incestual schema $G^a, b, c, d$. Further we exemplify the constraints required on fibring function to capture the semantics of interactions among modalities. The advantages of having a fibred approach is discussed in the final section.
    BibTeX:
    @inproceedings{jelia02,
      author = {Governatori, Guido and Padmanabhan, Vineet N. and Sattar, Abdul},
      title = {On Fibring Semantics for BDI Logics},
      booktitle = {Jelia 2002},
      publisher = {Springer-Verlag},
      year = {2002},
      pages = {198-210},
      url = {http://springerlink.metapress.com/index/XF6RY52PXMPD1YPJ}
    }
    
    Governatori, G., Padmanabhan, V. N. & Sattar, A. A Defeasible Logic of Policy-Based Intention (extended abstract) 2002 AI'02, pp. 723  inproceedings URL  
    BibTeX:
    @inproceedings{ai02,
      author = {Governatori, Guido and Padmanabhan, Vineet N. and Sattar, Abdul},
      title = {A Defeasible Logic of Policy-Based Intention (extended abstract)},
      booktitle = {AI'02},
      publisher = {Springer-Verlag},
      year = {2002},
      pages = {723},
      url = {http://springerlink.metapress.com/index/LT1RK1JT7CRYGUL9}
    }
    
    Governatori, G., Padmanabhan, V. N. & Sattar, A. A Defeasible Logic of Policy-based Intention 2002 Australasian Workshop on Computational Logic 2002: Proceedings, pp. 9-20  inproceedings  
    Abstract: Most of the theories on formalising intention interpret it as a unary modal operator in Kripkean semantics, which gives it a monotonic look. We argue that policy-based intentions tebratman1 exhibit non-monotonic behaviour which could be captured through a non-monotonic system like defeasible logic. The proposed technique alleviates most of the problems related to logical omniscience.
    BibTeX:
    @inproceedings{awcl02,
      author = {Governatori, Guido and Padmanabhan, Vineet N. and Sattar, Abdul},
      title = {A Defeasible Logic of Policy-based Intention},
      booktitle = {Australasian Workshop on Computational Logic 2002: Proceedings},
      publisher = {Department of Computer Science, The University of Melbourne},
      year = {2002},
      pages = {9-20}
    }
    
    Governatori, G., Palmirani, M., Riveret, Ré., Rotolo, A. & Sartor, G. Norm Modifications in Defeasible Logic 2005 Legal Knowledge and Information Systems, pp. 13-22  incollection  
    Abstract: This paper proposes a framework based on Defeasible Logic (DL) to reason about normative modifications. We show how to express them in DL and how the logic deals with conflicts between temporalised normative modifications. Some comments will be given with regard to the phenomenon of retroactivity.
    BibTeX:
    @incollection{jurix05,
      author = {Governatori, Guido and Palmirani, Monica and Riveret, Régis and Rotolo, Antonino and Sartor, Giovanni},
      title = {Norm Modifications in Defeasible Logic},
      booktitle = {Legal Knowledge and Information Systems},
      publisher = {IOS Press},
      year = {2005},
      pages = {13-22}
    }
    
    Governatori, G. & Pham, D. H. DR-CONTRACT: an architecture for e-contracts in defeasible logic 2009 International Journal of Business Process Intergration and Management
    Vol. 4 (3) , pp. 187-199 
    article DOI  
    Abstract: We introduce the DR-CONTRACT architecture to represent and reason on e-Contracts. The architecture extends the DR-device architecture by a deontic defeasible logic of violation. We motivate the choice for the logic and we show how to extend RuleML to capture the notions relevant to describe e-contracts for a monitoring perspective in Defeasible Logic.
    BibTeX:
    @article{ijbpim:coala,
      author = {Governatori, Guido and Pham, Duy Hoang},
      title = {DR-CONTRACT: an architecture for e-contracts in defeasible logic},
      journal = {International Journal of Business Process Intergration and Management},
      year = {2009},
      volume = {4},
      number = {3},
      pages = {187-199},
      doi = {http://dx.doi.org/10.1504/IJBPIM.2009.030985}
    }
    
    Governatori, G. & Rotolo, A. How Do Agents Comply with Norms? 2009 (09121) Normative Multi-Agent Systems  inproceedings URL  
    Abstract: The import of the notion of institution in the design of MASs requires to develop formal and efficient methods for modeling the interaction between agents' behaviour and normative systems. This paper discusses how to check whether agents' behaviour is compliant with the rules regulating them. The key point of our approach is that compliance is a relationship between two sets of specifications: the specifications for executing a process and the specifications regulating it. We propose a logic-based formalism for describing both the semantics of normative specifications and the semantics of compliance checking procedures.
    BibTeX:
    @inproceedings{normas09,
      author = {Guido Governatori and Antonino Rotolo},
      title = {How Do Agents Comply with Norms?},
      booktitle = {Normative Multi-Agent Systems},
      publisher = {Schloss Dagstuhl - Leibniz-Zentrum fuer Informatik, Germany},
      year = {2009},
      number = {09121},
      url = {http://drops.dagstuhl.de/opus/volltexte/2009/1909}
    }
    
    Governatori, G. & Rotolo, A. Changing Legal Systems: Abrogation and Annulment. Part II: Temporalised Defeasible Logic 2008 Proceedings of Normative Multi Agent Systems (NorMAS 2008  inproceedings  
    Abstract: In this paper we propose a temporal extension of Defeasible Logic to model legal modifications, such as abrogation and annulment. Hence, this framework overcomes the difficulty, discussed elsewhere tedeon-part1, of capturing these modification types using belief and base revision.
    BibTeX:
    @inproceedings{normas08,
      author = {Governatori, Guido and Rotolo, Antonino},
      title = {Changing Legal Systems: Abrogation and Annulment. Part II: Temporalised Defeasible Logic},
      booktitle = {Proceedings of Normative Multi Agent Systems (NorMAS 2008},
      year = {2008}
    }
    
    Governatori, G. & Rotolo, A. BIO Logical Agents: Norms, Beliefs, Intentions in Defeasible Logic 2007 Normative Multi-agent Systems  inproceedings URL  
    Abstract: In this paper we follow the BOID (Belief, Obligation, Intention, Desire) architecture to describe agents and agent types in Defeasible Logic. We argue, in particular, that the introduction of obligations can provide a new reading of the concepts of intention and intentionality. Then we examine the notion of social agent (i.e., an agent where obligations prevail over intentions) and discuss some computational and philosophical issues related to it. We show that the notion of social agent either requires more complex computations or has some philosophical drawbacks.
    BibTeX:
    @inproceedings{dagstuhl:social,
      author = {Governatori, Guido and Rotolo, Antonino},
      title = {BIO Logical Agents: Norms, Beliefs, Intentions in Defeasible Logic},
      booktitle = {Normative Multi-agent Systems},
      publisher = {Internationales Begegnungs- und Forschungszentrum fuer Informatik (IBFI), Schloss Dagstuhl, Germany},
      year = {2007},
      note = {[date of citation: 2007-01-01]},
      url = { http://drops.dagstuhl.de/opus/volltexte/2007/912/pdf/07122.GovernatoriGuido.Paper.912.pdf}
    }
    
    Governatori, G. & Rotolo, A. A Computational Framework for Non-Monotonic Agency, Institutionalised Power and Multi-Agent Systems 2003 Legal Knowledge and Information Systems, pp. 151-152  inproceedings URL  
    Abstract: This work provides a first computational framework to capture some of the theoretical intuitions developed by the present authors and other colleagues. More precisely, in this paper we propose a computationally oriented model of institutional agency based on Defeasible Logic. The focus here is on the notions of counts-as link and on those of attempt and of personal and direct action to realise states of affairs.
    BibTeX:
    @inproceedings{jurix03,
      author = {Governatori, Guido and Rotolo, Antonino},
      title = {A Computational Framework for Non-Monotonic Agency, Institutionalised Power and Multi-Agent Systems},
      booktitle = {Legal Knowledge and Information Systems},
      publisher = {IOS Press},
      year = {2003},
      pages = {151-152},
      url = {http://www.jurix.nl/pdf/j03-20.pdf}
    }
    
    Governatori, G. & Rotolo, A. A Defeasible Logic of Institutional Agency 2003 NRAC'03, pp. 97-104  inproceedings  
    Abstract: A non-monotonic logic of institutional agency is defined combining a computationally oriented non-monotonic system (Defeasible Logic) and intensional notions of agency.
    BibTeX:
    @inproceedings{nrac03,
      author = {Governatori, Guido and Rotolo, Antonino},
      title = {A Defeasible Logic of Institutional Agency},
      booktitle = {NRAC'03},
      year = {2003},
      pages = {97-104}
    }
    
    Governatori, G. & Rotolo, A. Norm Compliance in Business Process Modeling 2010 (6403) RuleML 2010: 4th International Web Rule Symposium, pp. 194-209  inproceedings DOI  
    Abstract: We investigate the concept of norm compliance in business process modeling. In particular we propose an extension of Formal Contract Logic (FCL), a combination of defeasible logic and a logic of violation, with a richer deontic language capable of capture many different facets of normative requirements. The resulting logic, called Process Compliance Logic (PCL), is able to capture both semantic compliance and structural compliance. This paper focuses on structural compliance, that is we show how PCL can capture obligations concerning the structure of a business process.
    BibTeX:
    @inproceedings{ruleml10compliance,
      author = {Governatori, Guido and Rotolo, Antonino},
      title = {Norm Compliance in Business Process Modeling},
      booktitle = {RuleML 2010: 4th International Web Rule Symposium},
      publisher = {Springer},
      year = {2010},
      number = {6403},
      pages = {194-209},
      doi = {http://dx.doi.org/10.1007/978-3-642-16289-3_17}
    }
    
    Governatori, G. & Rotolo, A. Labelled Modal Sequents 2000 (Scientific Report CS/00/001) Position Papers and Tutorials, TABLEAUX 2000, pp. 3-21  inproceedings  
    Abstract: In this paper we present a new labelled sequent calculus for modal logic. The proof method works with a more ``liberal'' modal language which allows inferential steps where different formulas refer to different labels without moving to a particular world and there computing if the consequence holds. World-paths can be composed, decomposed and manipulated through unification algorithms and formulas in different worlds can be compared even if they are sub-formulas which do not depend directly on the main connective. Accordingly, such a sequent system can provide a general definition of modal consequence relation. Finally, we briefly sketch a proof of the soundness and completeness results.
    BibTeX:
    @inproceedings{lms:tab2000,
      author = {Governatori, Guido and Rotolo, Antonino},
      title = {Labelled Modal Sequents},
      booktitle = {Position Papers and Tutorials, TABLEAUX 2000},
      publisher = {School of Computer Science, University of St Andrews},
      year = {2000},
      number = {Scientific Report CS/00/001},
      pages = {3-21}
    }
    
    Governatori, G. & Rotolo, A. An Algorithm for Business Process Compliance 2008 Legal Knowledge and Information Systems, pp. 186-191  inproceedings DOI  
    Abstract: This paper provides a novel mechanism to check whether business processes are compliant with business rules regulating them. The key point is that compliance is a relationship between two sets of specifications: the specifications for executing a business process and the specifications regulating it.
    BibTeX:
    @inproceedings{jurix08:compliance,
      author = {Governatori, Guido and Rotolo, Antonino},
      title = {An Algorithm for Business Process Compliance},
      booktitle = {Legal Knowledge and Information Systems},
      publisher = {IOS Press},
      year = {2008},
      pages = {186-191},
      doi = {http://dx.doi.org/10.3233/978-2-58603-952-3-186}
    }
    
    Governatori, G. & Rotolo, A. Representing Contracts Using RuleML 2004 Legal Knowledge and Information Systems, pp. 141-150  inproceedings URL  
    Abstract: This paper presents an approach for the specification and implementation of e-contracts for Web monitoring. This is done in the setting of RuleML. We argue that monitoring contract execution requires also a logical account of deontic concepts and of violations. Accordingly, RuleML is extended to cover these aspects.
    BibTeX:
    @inproceedings{jurix04,
      author = {Governatori, Guido and Rotolo, Antonino},
      title = {Representing Contracts Using RuleML},
      booktitle = {Legal Knowledge and Information Systems},
      publisher = {IOS Press},
      year = {2004},
      pages = {141-150},
      url = {http://www.jurix.nl/pdf/j04-16.pdf}
    }
    
    Governatori, G. & Rotolo, A. A Gentzen System for Reasoning with Contrary-To-Duty Obligations. A preliminary Study 2002 Deon'02, pp. 97-116  inproceedings  
    Abstract: In this paper we present a Gentzen system for reasoning with contrary-to-duty obligations. The intuition behind the system is that a contrary-to-duty is a special kind of normative exception. The logical machinery to formalize this idea is taken from substructural logics and it is based on the definition of a new non-classical connective capturing the notion of reparational obligation. Then the system is tested against well-known contrary-to-duty paradoxes.
    BibTeX:
    @inproceedings{deon2002,
      author = {Governatori, Guido and Rotolo, Antonino},
      title = {A Gentzen System for Reasoning with Contrary-To-Duty Obligations. A preliminary Study},
      booktitle = {$eon'02},
      publisher = {Imperial College},
      year = {2002},
      pages = {97-116}
    }
    
    Governatori, G. & Rotolo, A. A Conceptually Rich Model of Business Process Compliance 2010
    Vol. 110 7th Asia-Pacific Conference on Conceptual Modelling (APCCM 2010), pp. 3-12 
    inproceedings URL  
    Abstract: In this paper we extend the preliminary work developed elsewhere and investigate how to characterise many aspects of the compliance problem in business process modeling. We first define a formal and conceptually rich language able to represent, and reason about, chains of reparational obligations of various types. Second, we devise a mechanism for normalising a system of legal norms. Third, we specify a suitable language for business process modeling able to automate and optimise business procedures and to embed normative constraints. Fourth, we develop an algorithm for compliance checking and discuss some computational issues regarding the possibility of checking compliance runtime or of enforcing it at design time.
    BibTeX:
    @inproceedings{apccm2010,
      author = {Governatori, Guido and Rotolo, Antonino},
      title = {A Conceptually Rich Model of Business Process Compliance},
      booktitle = {7th Asia-Pacific Conference on Conceptual Modelling (APCCM 2010)},
      publisher = {ACS},
      year = {2010},
      volume = {110},
      pages = {3-12},
      url = {http://crpit.com/confpapers/CRPITV110Governatori.pdf}
    }
    
    Governatori, G. & Rotolo, A. Defeasible Logic: Agency, Intention and Obligation 2004 Deontic Logic in Computer Science, pp. 114-128  inproceedings URL  
    Abstract: We propose a computationally oriented non-monotonic multi-modal logic arising from the combination of agency, intention and obligation. We argue about the defeasible nature of these notions and then we show how to represent and reason with them in the setting of defeasible logic.
    BibTeX:
    @inproceedings{deon:04,
      author = {Governatori, Guido and Rotolo, Antonino},
      title = {Defeasible Logic: Agency, Intention and Obligation},
      booktitle = {Deontic Logic in Computer Science},
      publisher = {Springer},
      year = {2004},
      pages = {114-128},
      url = {http://springerlink.metapress.com/index/NN0UCU6140VV1HVL}
    }
    
    Governatori, G. & Rotolo, A. Changing Legal Systems: Abrogation and Annulment. Part I: Revision of Defeasible Theories 2008 9th International Conference on Deontic Logic in Computer Science (DEON2008), pp. 3-18  inproceedings DOI  
    Abstract: In this paper we investigate how to model legal abrogation and annulment in Defeasible Logic. We examine some options that embed in this setting, and similar rule-based systems, ideas from belief and base revision. In both cases, our conclusion is negative, which suggests to adopt a different logical model.
    BibTeX:
    @inproceedings{deon08,
      author = {Governatori, Guido and Rotolo, Antonino},
      title = {Changing Legal Systems: Abrogation and Annulment. Part I: Revision of Defeasible Theories},
      booktitle = {9th International Conference on Deontic Logic in Computer Science (DEON2008)},
      publisher = {Springer},
      year = {2008},
      pages = {3-18},
      doi = {http://dx.doi.org/10.1007/978-3-540-70525-3_2}
    }
    
    Governatori, G. & Rotolo, A. On the Complexity of Temporal Defeasible Logic 2010 13 International Workshop on Non-Monotonic Reasoning (NMR 2010)  inproceedings  
    Abstract: In this paper we investigate the complexity of temporal defeasible logic, and we propose an efficient algorithm to compute the extension of a temporalised defeasible theory. We motivate the logic showing how it can be used to model deadlines.
    BibTeX:
    @inproceedings{nmr10:temporal,
      author = {Governatori, Guido and Rotolo, Antonino},
      title = {On the Complexity of Temporal Defeasible Logic},
      booktitle = {13 International Workshop on Non-Monotonic Reasoning (NMR 2010)},
      year = {2010}
    }
    
    Governatori, G. & Rotolo, A. On the Axiomatization of Elgesem's Logic of Agency 2004 AiML 2004 -- Advances in Modal Logic, pp. 130-144  inproceedings URL  
    Abstract: In this paper we show that the Hilbert system of agency and ability presented by Dag Elgesem is incomplete with respect to the intended semantics. We argue that completeness result may be easily regained. Finally, we shortly discuss some issues related to the philosophical intuition behind his approach. This is done by examining Elgesem's modal logic of agency and ability using semantics with different flavours.
    BibTeX:
    @inproceedings{GovRot:04:AIML,
      author = {Governatori, Guido and Rotolo, Antonino},
      title = {On the Axiomatization of Elgesem's Logic of Agency},
      booktitle = {AiML 2004 -- Advances in Modal Logic},
      publisher = {Department of Computer Science, University of Manchester},
      year = {2004},
      pages = {130-144},
      url = {http://www.cs.man.ac.uk/cstechrep/index.html}
    }
    
    Governatori, G. & Rotolo, A. Changing legal systems: legal abrogations and annulments in Defeasible Logic 2010 Logic Journal of IGPL
    Vol. 18 (1) , pp. 157-194 
    article DOIURL  
    Abstract: In this paper we investigate how to represent and reason about legal abrogations and annulments in Defeasible Logic. We examine some options that embed in this setting, and in similar rule-based systems, ideas from belief and base revision. In both cases, our conclusion is negative, which suggests to adopt a different logical model. This model expresses temporal aspects of legal rules, and distinguishes between two main timelines, one internal to a given temporal version of the legal system, and another relative to how the legal system evolves over time. Accordingly, we propose a temporal extension of Defeasible Logic suitable to express this model and to capture abrogation and annulment. We show that the proposed framework overcomes the difficulties discussed in regard to belief and base revision, and is sufficiently flexible to represent many of the subtleties characterizing legal abrogations and annulments.
    BibTeX:
    @article{igpl10normchange,
      author = {Governatori, Guido and Rotolo, Antonino},
      title = {Changing legal systems: legal abrogations and annulments in Defeasible Logic},
      journal = {Logic Journal of IGPL},
      year = {2010},
      volume = {18},
      number = {1},
      pages = {157-194},
      url = {http://jigpal.oxfordjournals.org/cgi/content/abstract/jzp075v1},
      doi = {http://dx.doi.org/10.1093/jigpal/jzp075}
    }
    
    Governatori, G. & Rotolo, A. How Do Agents Comply with Norms? 2009
    Vol. 3 Web Intelligence and Intelligent Agent Technologies, 2009. WI-IAT '09. IEEE/WIC/ACM International Joint Conferences on, pp. 488-491 
    inproceedings DOI  
    Abstract: The import of the notion of institution in the design of MASs requires to develop formal and efficient methods for modeling the interaction between agents' behaviour and normative systems. This paper discusses how to check whether agents' behaviour complies with the rules regulating them. The key point of our approach is that compliance is a relationship between two sets of specifications: the specifications for executing a process and the specifications regulating it. We propose a formalism for describing both the semantics of normative specifications and the semantics of compliance checking procedures.
    BibTeX:
    @inproceedings{wliamas09,
      author = {Governatori, Guido and Rotolo, Antonino},
      title = {How Do Agents Comply with Norms?},
      booktitle = {Web Intelligence and Intelligent Agent Technologies, 2009. WI-IAT '09. IEEE/WIC/ACM International Joint Conferences on},
      publisher = {IEEE},
      year = {2009},
      volume = {3},
      pages = {488-491},
      doi = {http://dx.doi.org/10.1109/WI-IAT.2009.332}
    }
    
    Governatori, G. & Rotolo, A. A Computational Framework for Institutional Agency 2008 Artificial Intelligence and Law
    Vol. 16 (1) , pp. 25-52 
    article DOI  
    Abstract: This paper provides a computational framework, based on Defeasible Logic, to capture some aspects of institutional agency. Our background is Kanger-Lindahl-Pörn account of organised interaction, which describes this interaction within a multi-modal logical setting. This work focuses in particular on the notions of counts-as link and on those of attempt and of personal and direct action to realise states of affairs. We show how standard Defeasible Logic can be extended to represent these concepts: the resulting system preserves some basic properties commonly attributed to them. In addition, the framework enjoys nice computational properties, as it turns out that the extension of any theory can be computed in time linear to the size of the theory itself.
    BibTeX:
    @article{GovRot:AIL:06:counts-as,
      author = {Governatori, Guido and Rotolo, Antonino},
      title = {A Computational Framework for Institutional Agency},
      journal = {Artificial Intelligence and Law},
      year = {2008},
      volume = {16},
      number = {1},
      pages = {25-52},
      doi = {http://dx.doi.org/10.1007/s10506-007-9056-y}
    }
    
    Governatori, G. & Rotolo, A. BIO Logical Agents: Norms, Beliefs, Intentions in Defeasible Logic 2008 Journal of Autonomous Agents and Multi Agent Systems
    Vol. 17 (1) , pp. 36-69 
    article DOI  
    Abstract: In this paper we follow the BOID (Belief, Obligation, Intention, Desire) architecture to describe agents and agent types in Defeasible Logic. We argue, in particular, that the introduction of obligations can provide a new reading of the concepts of intention and intentionality. Then we examine the notion of social agent (i.e., an agent where obligations prevail over intentions) and discuss some computational and philosophical issues related to it. We show that the notion of social agent either requires more complex computations or has some philosophical drawbacks.
    BibTeX:
    @article{jaamas:bio,
      author = {Governatori, Guido and Rotolo, Antonino},
      title = {BIO Logical Agents: Norms, Beliefs, Intentions in Defeasible Logic},
      journal = {Journal of Autonomous Agents and Multi Agent Systems},
      year = {2008},
      volume = {17},
      number = {1},
      pages = {36-69},
      doi = {http://dx.doi.org/10.1007/s10458-008-9030-4}
    }
    
    Governatori, G. & Rotolo, A. Logic of Violations: A Gentzen System for Reasoning with Contrary-To-Duty Obligations 2006 Australasian Journal of Logic
    Vol. 4 , pp. 193-215 
    article URL  
    Abstract: In this paper we present a Gentzen system for reasoning with contrary-to-duty obligations. The intuition behind the system is that a contrary-to-duty is a special kind of normative exception. The logical machinery to formalise this idea is taken from substructural logics and it is based on the definition of a new non-classical connective capturing the notion of reparational obligation. Then the system is tested against well-known contrary-to-duty paradoxes.
    BibTeX:
    @article{ajl:ctd,
      author = {Governatori, Guido and Rotolo, Antonino},
      title = {Logic of Violations: A Gentzen System for Reasoning with Contrary-To-Duty Obligations},
      journal = {Australasian Journal of Logic},
      year = {2006},
      volume = {4},
      pages = {193-215},
      url = {http://www.philosophy.unimelb.edu.au/ajl/2006/2006_4.pdf}
    }
    
    Governatori, G. & Rotolo, A. On the Axiomatization of Elgesem's Logic of Agency and Ability 2005 Journal of Philosophical Logic
    Vol. 34 (4) , pp. 403-431 
    article DOI  
    Abstract: In this paper we show that the Hilbert system of agency and ability presented by Dag Elgesem is incomplete with respect to the intended semantics. We argue that completeness result may be easily regained. Finally, we shortly discuss some issues related to the philosophical intuition behind his approach. This is done by examining Elgesem's modal logic of agency and ability using semantics with different flavours.
    BibTeX:
    @article{elgesem:JPL,
      author = {Governatori, Guido and Rotolo, Antonino},
      title = {On the Axiomatization of Elgesem's Logic of Agency and Ability},
      journal = {Journal of Philosophical Logic},
      year = {2005},
      volume = {34},
      number = {4},
      pages = {403-431},
      doi = {http://dx.doi.org/10.1007/s10992-004-6368-1}
    }
    
    Governatori, G. & Antonino, R. Justice Delayed Is Justice Denied: Logics for a Temporal Account of Reparations and Legal Compliance 2011 (LNCS) CLIMA XII, 12th International Workshop on Computational Logic and Multi-Agent Sytems  inproceedings  
    Abstract: In this paper we extend the logic of violation proposed by Governatori and Rotolo with time, more precisely, we temporalise that logic. The resulting system allows us to capture many subtleties of the concept of legal compliance. In particular, the formal characterisation of compliance can handle different types of legal obligation and different temporal constraints over them. The logic is also able to represent, and reason about, chains of reparative obligations, since in many cases the fulfillment of these types of obligation still amount to legally acceptable situations.
    BibTeX:
    @inproceedings{clima,
      author = {Governatori, Guido and Rotolo Antonino},
      title = {Justice Delayed Is Justice Denied: Logics for a Temporal Account of Reparations and Legal Compliance},
      booktitle = {CLIMA XII, 12th International Workshop on Computational Logic and Multi-Agent Sytems},
      publisher = {Springer},
      year = {2011},
      number = {LNCS}
    }
    
    Governatori, G., Rotolo, A. & Padmanabhan, V. The Cost of Social Agents 2006 5th International Conference on Autonomous Agents and Multi-Agent Systems, pp. 513-520  inproceedings DOI  
    Abstract: In this paper we follow the BOID (Belief, Obligation, Intention, Desire) architecture to describe agents and agent types in Defeasible Logic. We argue that the introduction of obligations can provide a new reading of the concepts of intention and intentionality. Then we examine the notion of social agent (i.e., an agent where obligations prevail over intentions) and discuss some computational and philosophical issues related to it. We show that the notion of social agent either requires more complex computations or has some philosophical drawbacks.
    BibTeX:
    @inproceedings{aamas06cost,
      author = {Governatori, Guido and Rotolo, Antonino and Padmanabhan, Vineet},
      title = {The Cost of Social Agents},
      booktitle = {5th International Conference on Autonomous Agents and Multi-Agent Systems},
      publisher = {ACM Press},
      year = {2006},
      pages = {513-520},
      doi = {http://dx.doi.org/10.1145/1160633.1160728?}
    }
    
    Governatori, G., Rotolo, A., Riveret, Ré., Palmirani, M. & Sartor, G. Variations of Temporal Defeasible Logic for Modelling Norm Modifications 2007 Proceedings of 11th International Conference on Artificial Intelligence and Law, pp. 155-159  inproceedings DOI  
    Abstract: This paper proposes some variants of Temporal Defeasible Logic (TDL) to reason about normative modifications. These variants make it possible to differentiate cases in which, for example, modifications at some time change legal rules but their conclusions persist afterwards from cases where also their conclusions are blocked.
    BibTeX:
    @inproceedings{icail07:modifications,
      author = {Governatori, Guido and Rotolo, Antonino and Riveret, Régis and Palmirani, Monica and Sartor, Giovanni},
      title = {Variations of Temporal Defeasible Logic for Modelling Norm Modifications},
      booktitle = {Proceedings of 11th International Conference on Artificial Intelligence and Law},
      publisher = {ACM Press},
      year = {2007},
      pages = {155-159},
      doi = {http://dx.doi.org/10.1145/1276318.1276347}
    }
    
    Governatori, G., Rotolo, A. & Rubino, R. Implementing Temporal Defeasible Logic for Modeling Legal Reasoning 2010
    Vol. 6284 New Frontiers in Artificial Intelligence: JSAI-isAI 2009 Workshops, pp. 45-58 
    inproceedings DOI  
    Abstract: In this paper we briefly present an efficient implementation of temporal defeasible logic, and we argue that it can be used to efficiently capture the the legal concepts of persistence, retroactivity and periodicity. In particular, we illustrate how the system works with a real life example of a regulation.
    BibTeX:
    @inproceedings{jurisin09,
      author = {Governatori, Guido and Rotolo, Antonino and Rubino, Rossella},
      title = {Implementing Temporal Defeasible Logic for Modeling Legal Reasoning},
      booktitle = {New Frontiers in Artificial Intelligence: JSAI-isAI 2009 Workshops},
      publisher = {Springer},
      year = {2010},
      volume = {6284},
      pages = {45-58},
      doi = {http://dx.doi.org/10.1007/978-3-642-14888-0_5}
    }
    
    Governatori, G., Rotolo, A. & Sadiq, S. A Model of Dynamic Resource Allocation in Workflow Systems 2004 Database Technology 2004, pp. 197-206  inproceedings URL  
    Abstract: Current collaborative work environments are characterized by dynamically changing organizational structures. Although there have been several efforts to refine work distribution, especially in workflow management, most literature assumes a static database approach which captures organizational roles, groups and hierarchies and implements a dynamic roles based agent assignment protocol. However, in practice only partial information may be available for organizational models, and in turn a large number of exceptions may emerge at the time of work assignment. In this paper we present an organizational model based on a policy based normative system. The model is based on a combination of an intensional logic of agency and a flexible, but computationally feasible, non-monotonic formalism (Defeasible Logic). Although this paper focuses on the model specification, the proposed approach to modelling agent societies provides a means of reasoning with partial and unpredictable information as is typical of organizational agents in workflow systems.
    BibTeX:
    @inproceedings{adc04grs,
      author = {Governatori, Guido and Rotolo, Antonino and Sadiq, Shazia},
      title = {A Model of Dynamic Resource Allocation in Workflow Systems},
      booktitle = {Database Technology 2004},
      publisher = {ACS},
      year = {2004},
      pages = {197-206},
      url = {http://crpit.com/confpapers/CRPITV27Governatori.pdf}
    }
    
    Governatori, G., Rotolo, A. & Sartor, G. Temporalised Normative Positions in Defeasible Logic 2005 10th International Conference on Artificial Intelligence and Law (ICAIL05), pp. 25-34  inproceedings DOI  
    Abstract: We propose a computationally oriented non-monotonic multi-modal logic arising from the combination of temporalised agency and temporalised normative positions. We argue about the defeasible nature of these notions and then we show how to represent and reason with them in the setting of Defeasible Logic.
    BibTeX:
    @inproceedings{icail05,
      author = {Governatori, Guido and Rotolo, Antonino and Sartor, Giovanni},
      title = {Temporalised Normative Positions in Defeasible Logic},
      booktitle = {10th International Conference on Artificial Intelligence and Law (ICAIL05)},
      publisher = {ACM Press},
      year = {2005},
      pages = {25-34},
      doi = {http://dx.doi.org/10.1145/1165485.1165490}
    }
    
    Governatori, G. & Sadiq, S. The Journey to Business Process Compliance 2009 Handbook of Research on BPM, pp. 426-454  incollection  
    Abstract: It is a typical scenario that many organisations have their business processes specified independently of their business obligations (which includes contractual obligations to business partners, as well as obligations a business has to fulfil against regulations and industry standards). This is because of the lack of guidelines and tools that facilitate derivation of processes from contracts but also because of the traditional mindset of treating contracts separately from business processes. This chapter will provide a solution to one specific problem that arises from this situation, namely the lack of mechanisms to check whether business processes are compliant with business contracts. The chapter begins by defining the space for business process compliance and the eco-system for ensuring that process are compliant. The key point is that compliance is a relationship between two sets of specifications: the specifications for executing a business process and the specifications regulating a business. The central part of the chapter focuses on a logic based formalism for describing both the semantics of normative specifications and the semantics of compliance checking procedures.
    BibTeX:
    @incollection{HandbookBPM:IGI,
      author = {Governatori, Guido and Sadiq, Shazia},
      title = {The Journey to Business Process Compliance},
      booktitle = {Handbook of Research on BPM},
      publisher = {IGI Global},
      year = {2009},
      pages = {426-454}
    }
    
    Governatori, G. & Sartor, G. Burdens of Proof in Monological Argumentation 2010 Legal Knowledge and Information Systems JURIX 2010: The Twenty-Third Annual Conference  inproceedings  
    Abstract: We shall argue that burdens of proof are relevant also to monological reasoning, i.e., for deriving the conclusions of a knowledge-base allowing for conflicting arguments. Reasoning with burdens of proof can provide a useful extension of current argument-based non-monotonic logics, at least a different perspective on them. Firstly we shall provide an objective characterisation of burdens of proof, assuming that burdens concerns rule antecedents (literals in the body of rules), rather than agents. Secondly, we shall analyse the conditions for a burden to be satisfied, by considering credulous or skeptical derivability of the concerned antecedent or of its complement. Finally, we shall develop a method for developing inferences out of a knowledge base merging rules and proof burdens in the framework of defeasible logic.
    BibTeX:
    @inproceedings{jurix10burden,
      author = {Governatori, Guido and Sartor, Giovanni},
      title = {Burdens of Proof in Monological Argumentation},
      booktitle = {Legal Knowledge and Information Systems JURIX 2010: The Twenty-Third Annual Conference},
      publisher = {IOS Press},
      year = {2010}
    }
    
    Governatori, G. & Stranieri, A. Towards the Application of Association Rules for Defeasible Rules Discovery 2001 Legal Knowledge and Information Systems, pp. 63-75  inproceedings URL  
    Abstract: In this paper we investigate the feasibility of Knowledge Discovery from Database (KDD) in order to facilitate the discovery of defeasible rules that represent the ratio decidendi underpinning legal decision making. Moreover we will argue in favour of Defeasible Logic as the appropriate formal system in which the extracted principles should be encoded.
    BibTeX:
    @inproceedings{jurix,
      author = {Governatori, Guido and Stranieri, Andrew},
      title = {Towards the Application of Association Rules for Defeasible Rules Discovery},
      booktitle = {Legal Knowledge and Information Systems},
      publisher = {IOS Press},
      year = {2001},
      pages = {63-75},
      url = {http://www.jurix.nl/pdf/j01-06.pdf}
    }
    
    Governatori, G. & Terenziani, P. Temporal Extension of Defeasible Logic 2007 Proceedings of the IJCAI'07 Workshop on Spatial And Temporal Reasoning  inproceedings  
    Abstract: In this paper, we extend defeasible logic (a computationally-oriented non-monotonic logic) in order to deal with temporalised rules. In particular, we extend the logic to cope with durative facts, as well as with delays between the antecedent and the consequent of rules. We showed that the extended temporalised framework is suitable to model different types of causal relations which have been identified by the specialised literature. Finally, we also demonstrate that the computational properties of the original logic are still retained by the extended approach.
    BibTeX:
    @inproceedings{ijcai:07:temporal,
      author = {Governatori, Guido and Terenziani, Paolo},
      title = {Temporal Extension of Defeasible Logic},
      booktitle = {Proceedings of the IJCAI'07 Workshop on Spatial And Temporal Reasoning},
      year = {2007}
    }
    
    Governatori, G. & Terenziani, P. Temporal Extensions to Defeasible Logic 2007 20th Australian Joint Conference on Artificial Intelligence, AI 2007, pp. 476-485  inproceedings DOI  
    Abstract: In this paper, we extend Defeasible Logic (a computationally-oriented non-monotonic logic) in order to deal with temporalised rules. In particular, we extend the logic to cope with durative facts, as well as with delays between the antecedent and the consequent of rules. We showed that the extended temporalised framework is suitable to model different types of causal relations which have been identified by the specialised literature. We also prove that the computational properties of the original logic are still retained by the extended approach.
    BibTeX:
    @inproceedings{austai07:causality,
      author = {Governatori, Guido and Terenziani, Paolo},
      title = {Temporal Extensions to Defeasible Logic},
      booktitle = {20th Australian Joint Conference on Artificial Intelligence, AI 2007},
      publisher = {Springer},
      year = {2007},
      pages = {476-485},
      doi = {http://dx.doi.org/10.1007/978-3-540-76928-6_49}
    }
    
    Governatori, G., Thakur, S. & Pham, D. H. A Compliance Model of Trust 2008 Legal Knowledge and Information Systems, pp. 118-127  inproceedings DOI  
    Abstract: We present a model of past interaction trust model based on compliance of expected behaviours.
    BibTeX:
    @inproceedings{jurix08:trust,
      author = {Governatori, Guido and Thakur, Subhasis and Pham, Duy Hoang},
      title = {A Compliance Model of Trust},
      booktitle = {Legal Knowledge and Information Systems},
      publisher = {IOS Press},
      year = {2008},
      pages = {118-127},
      doi = {http://dx.doi.org/10.3233/978-2-58603-952-3-118}
    }
    
    Hoffmann, Jö., Weber, I. & Governatori, G. On Compliance Checking for Clausal Constraints in Annotated Process Models 2009 Information Systems Frontieres   article DOI  
    Abstract: Compliance management is important in several industry sectors where there is a high incidence of regulatory control. It must be ensured that business practices, as reflected in business processes, comply with the rules. Such compliance checks are challenging due to (1) the different life cycles of rules and processes, and (2) their disparate representations. (1) requires retrospective checking of process models. To address (2), we herein devise a framework where processes are annotated to capture the semantics of task execution, and compliance is checked against a set of constraints posing restrictions on the desirable process states. Each constraint is a clause, i.e., a disjunction of literals. If a process can reach a state that falsifies all literals of one of the constraints, then that constraint is violated in that state, and indicates non-compliance.
    Naively, such compliance can be checked by enumerating all reachable states. Since long waiting times are undesirable, it is important to develop efficient (low-order polynomial time) algorithms that (a) perform exact compliance checking for restricted cases, or (b) perform approximate compliance checking for more general cases. Herein, we observe that methods of both kinds can be defined as a natural extension of our earlier work on semantic business process validation. We devise one method of type (a), and we devise two methods of type (b); both are based on similar restrictions to the processes, where the restrictions made by methods (b) are a subset of those made by method (a). The approximate methods each guarantee either of soundness (finding only non-compliance instances) or completeness (finding all non-compiant states). We describe how one can trace the state evolution back to the process activities which caused the (potential) non-compliant states, and hence provide the user with an error diagnosis.
    BibTeX:
    @article{isf09compliance,
      author = {Hoffmann, Jörg and Weber, Ingo and Governatori, Guido},
      title = {On Compliance Checking for Clausal Constraints in Annotated Process Models},
      journal = {Information Systems Frontieres},
      year = {2009},
      doi = {http://dx.doi.org/10.1007/s10796-009-9179-7}
    }
    
    Johnston, B. & Governatori, G. Induction of Defeasible Logic Theories in the Legal Domain 2003 Procedings of the 9th International Conference on Artificial Intelligence and Law, pp. 204-213  inproceedings DOI  
    Abstract: The market for intelligent legal information systems remains relatively untapped and while this might be interpreted as an indication that it is simply impossible to produce a system that satisfies the needs of the legal community, an analysis of previous attempts at producing such systems reveals a common set of deficiencies that in-part explain why there have been no overwhelming successes to date. Defeasible logic, a logic with proven successes at representing legal knowledge, seems to overcome many of these deficiencies and is a promising approach to representing legal knowledge. Unfortunately, an immediate application of technology to the challenges in this domain is an expensive and computationally intractable problem. So, in light of the benefits, we seek to find a practical algorithm that uses heuristics to discover an approximate solution. As an outcome of this work, we have developed an algorithm that integrates defeasible logic into a decision support system by automatically deriving its knowledge from databases of precedents. Experiments with the new algorithm are very promising -- delivering results comparable to and exceeding other approaches.
    BibTeX:
    @inproceedings{icail03,
      author = {Johnston, Benjamin and Governatori, Guido},
      title = {Induction of Defeasible Logic Theories in the Legal Domain},
      booktitle = {Procedings of the 9th International Conference on Artificial Intelligence and Law},
      publisher = {ACM Press},
      year = {2003},
      pages = {204-213},
      doi = {http://dx.doi.org/10.1145/1047788.1047834}
    }
    
    Johnston, B. & Governatori, G. An algorithm for the induction of defeasible logic theories from databases 2003 Database Technology 2003, pp. 75-83  inproceedings URL  
    Abstract: Defeasible logic is a non-monotonic logic with applications in rule-based domains such as law. To ease the development and improve the accuracy of expert systems based on defeasible logic, it is desirable to automatically induce a theory of the logic from a training set of precedent data. Empirical evidence suggests that minimal theories that describe the training set tend to be more faithful representations of reality. We show via transformation from the hitting set problem that this global minimization problem is intractable, belonging to the class of NP optimisation problems. Given the inherent difficulty of finding the optimal solution, we instead use heuristics and demonstrate that a best-first, greedy, branch and bound algorithm can be used to find good theories in short time. This approach displays significant improvements in both accuracy and theory size as compared to recent work in the area that post-processed the output of an Aprori association rule-mining algorithm, with comparable execution times.
    BibTeX:
    @inproceedings{adc03,
      author = {Johnston, Benjamin and Governatori, Guido},
      title = {An algorithm for the induction of defeasible logic theories from databases},
      booktitle = {Database Technology 2003},
      publisher = {ACS},
      year = {2003},
      pages = {75-83},
      url = {http://www.jrpit.flinders.edu.au/confpapers/CRPITV17Johnston.pdf}
    }
    
    Kamada, A., Governatori, G. & Sadiq, S. Transformation of SBVR Compliant Business Rules to Executable FCL Rules 2010 (6403) RuleML 2010: 4th International Web Rule Symposium, pp. 153-161  inproceedings DOI  
    Abstract: The main source of changing requirements of the dynamic business environment is response to changes in regulations and contracts towards which businesses are obligated to comply. At the same time, many organizations have their business processes specified independently of their business obligations (which include adherence to contracts laws and regulations). Thus, the problem of mapping business changes into computational systems becomes much more complicated. In this paper we address the problem by providing an automated transformation of business rules into a formal language capable of directly mapping onto executable specifications. The model transformation is consistent with MDA/MOF/QVT concepts using ATL to perform the mapping. Business rules are compliant to SBVR metamodel, and are transformed into FCL, a logic based formalism, known to have a direct mapping onto executable specifications. Both, source and target rules are based on principles of deontic logic, the core of which are obligations, permissions and prohibitions.
    BibTeX:
    @inproceedings{ruleml10sbvr,
      author = {Kamada, Aqueo and Governatori, Guido and Sadiq, Shazia},
      title = {Transformation of SBVR Compliant Business Rules to Executable FCL Rules},
      booktitle = {RuleML 2010: 4th International Web Rule Symposium},
      publisher = {Springer},
      year = {2010},
      number = {6403},
      pages = {153-161},
      doi = {http://dx.doi.org/10.1007/978-3-642-16289-3_14}
    }
    
    Kontopoulos, E., Bassiliades, N., Governatori, G. & Antoniou, G. Extending a Defeasible Reasoner with Modal and Deontic Logic Operators 2008 2008 IEEE/WIC/ACM International Conference on Web Intelligence and Intelligent Agent Technology, pp. 626-629  inproceedings DOI  
    Abstract: Defeasible logic is a non-monotonic formalism that deals with incomplete and conflicting information. Modal logic deals with necessity and possibility, exhibiting defeasibility; thus, it is possible to combine defeasible logic with modal operators. This paper reports on the extension of the DR-DEVICE defeasible reasoner with modal and deontic logic operators. The aim is a practical defeasible reasoner that will take advantage of the expressiveness of modal logics and the flexibility to define diverse agent types and behaviors.
    BibTeX:
    @inproceedings{wliamas08kontopoulos,
      author = {Kontopoulos, Efsrations and Bassiliades, Nick and Governatori, Guido and Antoniou, Grigoris},
      title = {Extending a Defeasible Reasoner with Modal and Deontic Logic Operators},
      booktitle = {2008 IEEE/WIC/ACM International Conference on Web Intelligence and Intelligent Agent Technology},
      publisher = {IEEE Press},
      year = {2008},
      pages = {626-629},
      doi = {http://dx.doi.org/10.1109/WIIAT.2008.164}
    }
    
    Kravari, K., Kastori, G., Bassiliades, N. & Governatori, G. A Contract Agreement Policy-based Workflow Methodology for Agents Interacting in the Semantic Web 2010 (6403) RuleML 2010: 4th International Web Rule Symposium, pp. 225-239  inproceedings DOI  
    Abstract: The Semantic Web aims at automating Web content understanding and user request satisfaction. Intelligent agents assist towards this by performing complex actions on behalf of their users into real-life applications, such as e-Contracts, which make transactions simple by modeling the processes involved. This paper, presents a policy-based workflow methodology for efficient contract agreement among agents interacting in the Semantic Web. In addition, we present the integration of this methodology into a multi-agent knowledge-based framework, providing flexibility, reusability and interoperability of behavior between agents. The main advantage of our approach is that it provides a safe, generic, and reusable framework for modeling and monitoring e-Contract agreements, which could be used for different types of on-line transactions among agents. Furthermore, our framework is based on Semantic Web and FIPA standards, to maximize interoperability and reusability. Finally, an e-Commerce contract negotiation scenario is presented that illustrates the usability of the approach.
    BibTeX:
    @inproceedings{ruleml10agents,
      author = {Kravari, Kalliopi and Kastori, GrammatipEirini and Bassiliades, Nick and Governatori, Guido},
      title = {A Contract Agreement Policy-based Workflow Methodology for Agents Interacting in the Semantic Web},
      booktitle = {RuleML 2010: 4th International Web Rule Symposium},
      publisher = {Springer},
      year = {2010},
      number = {6403},
      pages = {225-239},
      doi = {http://dx.doi.org/10.1007/978-3-642-16289-3_19}
    }
    
    Lam, H.-P. & Governatori, G. On the problem of computing Ambiguity Propagation and Well-Founded Semantics in Defeasible Logic 2010 (6403) RuleML 2010: 4th International Web Rule Symposium, pp. 119-127  inproceedings DOI  
    Abstract: In this paper we present the well founded variants of ambiguityblocking and ambiguity propagating defeasible logics. We also show how to extend SPINdle, a state of the art, defeasible logic implementation to handle all such variants of defeasible logic.
    BibTeX:
    @inproceedings{ruleml10wellfounded,
      author = {Lam, Ho-Pun and Governatori, Guido},
      title = {On the problem of computing Ambiguity Propagation and Well-Founded Semantics in Defeasible Logic},
      booktitle = {RuleML 2010: 4th International Web Rule Symposium},
      publisher = {Springer},
      year = {2010},
      number = {6403},
      pages = {119-127},
      doi = {http://dx.doi.org/10.1007/978-3-642-16289-3_11}
    }
    
    Lam, H.-P. & Governatori, G. The Making of SPINdle 2009 (5858) Rule Representation, Interchange and Reasoning on the Web  inproceedings DOI  
    BibTeX:
    @inproceedings{ruleml09:spindle,
      author = {Lam, Ho-Pun and Governatori, Guido},
      title = {The Making of SPINdle},
      booktitle = {Rule Representation, Interchange and Reasoning on the Web},
      publisher = {Springer},
      year = {2009},
      number = {5858},
      doi = {http://dx.doi.org/10.1007/978-3-642-04985-9_29}
    }
    
    Lam, H.-P., Thakur, S., Governatori, G. & Sattar, A. A Model to Coordinate UAVs in Urban Environments Using Defeasible Logic 2009 (549) Proceedings of the 3rd International RuleML-2009 Challenge, pp. 7.1-7.8  inproceedings  
    Abstract: In this paper we show how a non-monotonic rule based system (defeasible logic) can be integrated with numerical computation engines. To this end we simulate a physical system from which we obtain numerical information. The physical system perceives information from its environment and it sends some predicates which are used by the defeasible logic reasoning engine to make decisions and then these decisions are realized by the physical system as it takes action based on the decision made by the reasoning engine. We consider a scenario where UAVs have to navigate through an urban environment. The UAVs are autonomous and there is no centralized control. The goal of the UAVs is to navigate without any collisions with each other or with any building. In case of a possible collision, the concerned UAVs communicate with each other and use background knowledge or some travel guidelines to resolve the conflicts.
    BibTeX:
    @inproceedings{Lam:rule09:challenge,
      author = {Lam, Ho-Pun and Thakur, Subhasis and Governatori, Guido and Sattar, Abdul},
      title = {A Model to Coordinate UAVs in Urban Environments Using Defeasible Logic},
      booktitle = {Proceedings of the 3rd International RuleML-2009 Challenge},
      year = {2009},
      number = {549},
      pages = {7.1-7.8}
    }
    
    Lu, R., Sadiq, S. & Governatori, G. A Framework for Utilizing Preferred Work Practice for Business Process Evolution 2007 Technologies for Business Information Systems, pp. 39-50  incollection DOI  
    Abstract: Many Business Process Management (BPM) systems provide best practice process models, both generic as well as for specific industry sectors. However, it is often the variance from template solutions that provide organizations with intellectual capital and competitive differentiation. Although variance must comply with various contractual, regulatory and operational constraints, it is still an important information resource, representing preferred work practices. In this paper, we present a framework that utilizes desired work practice to support business process evolution. The framework on one hand provides the ability to use domain expert knowledge and experience to tailor individual process instances according to case specific requirements; and on the other, provides a means of using this knowledge through learning techniques to guide subsequent process refinements.
    BibTeX:
    @incollection{RuopSadGov:07:framework,
      author = {Lu, Ruopeng and Sadiq, Shazia and Governatori, Guido},
      title = {A Framework for Utilizing Preferred Work Practice for Business Process Evolution},
      booktitle = {Technologies for Business Information Systems},
      publisher = {Springer},
      year = {2007},
      pages = {39-50},
      doi = {http://dx.doi.org/10.1007/1-4020-5634-6_4}
    }
    
    Lu, R., Sadiq, S. & Governatori, G. Utilizing Successful Work Practice for Business Process Evolution 2006 Business Information Systems (BIS 2006), pp. 58-76  inproceedings  
    Abstract: Business process management (BPM) has emerged as a dominant technology in current enterprise systems and business solutions. However, business processes are always evolving in current dynamic business environments where requirements and goals are constantly changing. Whereas literature reports on the importance of domain experts in process modelling and adaptations, current solutions have not addressed this issue effectively. In this paper, we present a framework that utilizes successful work practice to support business process evolution. The framework on one hand provides the ability to use domain expert knowledge and experience to tailor individual process instances according to case specific requirements; and on the other, provides a means of using this knowledge through learning techniques to guide subsequent process changes.
    BibTeX:
    @inproceedings{LuSadGov:06:Utilizing,
      author = {Lu, Ruopeng and Sadiq, Shazia and Governatori, Guido},
      title = {Utilizing Successful Work Practice for Business Process Evolution},
      booktitle = {Business Information Systems (BIS 2006)},
      publisher = {Bonner Köllen Verlag},
      year = {2006},
      pages = {58-76}
    }
    
    Lu, R., Sadiq, S. & Governatori, G. Compliance Aware Business Process Design 2007 3rd International Workshop on Business Process Design (BPD'07), pp. 120-131  inproceedings DOI  
    Abstract: Historically, business process design has been driven by business objectives, specifically process improvement. However this cannot come at the price of control objectives which stem from various legislative, standard and business partnership sources. Ensuring the compliance to regulations and industrial standards is an increasingly important issue in the design of business processes. In this paper, we advocate that control objectives should be addressed at an early stage, i.e., design time, so as to minimize the problems of runtime compliance checking and consequent violations and penalties. To this aim, we propose supporting mechanisms for business process designers. This paper specifically presents a support method which allows the process designer to quantitatively measure the compliance degree of a given process model against a set of control objectives. This will allow process designers to comparatively assess the compliance degree of their design as well as be better informed on the cost of non-compliance.
    BibTeX:
    @inproceedings{LuSadGov:bpd07,
      author = {Lu, Ruopeng and Sadiq, Shazia and Governatori, Guido},
      title = {Compliance Aware Business Process Design},
      booktitle = {3rd International Workshop on Business Process Design (BPD'07)},
      publisher = {Springer},
      year = {2007},
      pages = {120-131},
      doi = {http://dx.doi.org/10.1007/978-3-540-78238-4_14}
    }
    
    Lu, R., Sadiq, S. & Governatori, G. On Managing Business Processes Variants 2009 Data and Knowledge Engineering
    Vol. 68 (7) , pp. 642-664 
    article DOI  
    Abstract: Variance in business process execution can be the result of several situations, such as disconnection between documented models and business operations, workarounds in spite of process execution engines, dynamic change and exception handling, flexible and ad-hoc requirements, and collaborative and/or knowledge intensive work. It is imperative that effective support for managing process variances be extended to organizations mature in their BPM (Business Process Management) uptake so that they can ensure organization wide consistency, promote reuse and capitalize on their BPM investments. This paper presents an approach for managing business processes that is conducive to dynamic change and the need for flexibility in execution. The approach is based on the notion of process constraints. It further provides a technique for effective utilization of the adaptations manifested in process variants. In particular, we will present a facility for discovery of preferred variants through effective search and retrieval based on the notion of process similarity, where multiple aspects of the process variants are compared according to specific query requirements. The advantage of this approach is the ability to provide a quantitative measure for the similarity between process variants, which further facilitates various BPM activities such as process reuse, analysis and discovery.
    BibTeX:
    @article{dke:09:variants,
      author = {Lu, Ruopeng and Sadiq, Shazia and Governatori, Guido},
      title = {On Managing Business Processes Variants},
      journal = {Data and Knowledge Engineering},
      year = {2009},
      volume = {68},
      number = {7},
      pages = {642-664},
      doi = {http://dx.doi.org/10.1016/j.datak.2009.02.009}
    }
    
    Lu, R., Sadiq, S. & Governatori, G. Measurement of Compliance Distance in Business Processes 2008 Information Systems Management
    Vol. 25 (4) , pp. 344-355 
    article DOI  
    Abstract: Ensuring that work practice is compliant to regulations and industrial standards is an increasingly important issue in business systems. Whereas as an understanding of control objectives that stem from various legislative, standard and contractual sources may be found at strategic or tactical levels, an assessment of their effective adoption in operational practices is extremely hard. In this paper, we propose a method for assessing the level of compliance in business work practice. The method builds upon business process management platforms, and provides the ability to objectively measure the compliance distance of existing processes within the organization. This in turn empowers process designers and business analysts to quantify the effort required to achieve a compliant process.
    BibTeX:
    @article{ism08,
      author = {Lu, Ruopeng and Sadiq, Shazia and Governatori, Guido},
      title = {Measurement of Compliance Distance in Business Processes},
      journal = {Information Systems Management},
      year = {2008},
      volume = {25},
      number = {4},
      pages = {344-355},
      doi = {http://dx.doi.org/10.1080/10580530802384613}
    }
    
    Lu, R., Sadiq, S., Governatori, G. & Yang, X. Defining Adaptation Constraints for Business Process Variants 2009 12th International Conference on Business Information Systems, pp. 145-156  inproceedings DOI  
    Abstract: In current dynamic business environment, it has been argued that certain characteristics of ad-hocism in business processes are desirable. Such business processes typically have a very large number of instances, where design decisions for each process instance may be made at runtime. In these cases, predictability and repetitiveness cannot be counted upon, as the complete process knowledge used to define the process model only becomes available at the time after a specific process instance has been instantiated. The basic premise is that for a class of business processes it is possible to specify a small number of essential constraints at design time, but allow for a large number of execution possibilities at runtime. The objective of this paper is to conceptualise a set of constraints for process adaptation at instance level. Based on a comprehensive modelling framework, business requirements can be transformed to a set of minimal constraints, and the support for specification of process constraints and techniques to ensure constraint quality are developed.
    BibTeX:
    @inproceedings{bis:09:variants,
      author = {Lu, Ruopeng and Sadiq, Shazia and Governatori, Guido and Yang, Xiaoping},
      title = {Defining Adaptation Constraints for Business Process Variants},
      booktitle = {12th International Conference on Business Information Systems},
      publisher = {Springer},
      year = {2009},
      pages = {145-156},
      doi = {http://dx.doi.org/10.1007/978-3-642-01190-0_13}
    }
    
    Lu, R., Sadiq, S., Padmanabhan, V. & Governatori, G. Using a Temporal Constraint Network for Business Process Execution 2006 Seventeenth Australasian Database Conference (ADC2006), pp. 157-166  inproceedings URL  
    Abstract: Business process management (BPM) has emerged as a dominant technology in current enterprise systems and business solutions. However, the technology continues to face challenges in coping with dynamic business environments where requirements and goals are constantly changing. In this paper, we present a modelling framework for business processes that is conducive to dynamic change and the need for flexibility in execution. This framework is based on the notion of process constraints. Process constraints may be specified for any aspect of the process, such as task selection, control flow, resource allocation, etc. Our focus in this paper is on a set of scheduling constraints that are specified through a temporal constraint network. We will demonstrate how this specification can lead to increased flexibility in process execution, while maintaining a desired level of control. A key feature and strength of the approach is to use the power of constraints, while still preserving the intuition and visual appeal of graphical languages for process modelling.
    BibTeX:
    @inproceedings{adc06ruopeng,
      author = {Lu, Ruopeng and Sadiq, Shazia and Padmanabhan, Vineet and Governatori, Guido},
      title = {Using a Temporal Constraint Network for Business Process Execution},
      booktitle = {Seventeenth Australasian Database Conference (ADC2006)},
      publisher = {ACS},
      year = {2006},
      pages = {157-166},
      url = {http://crpit.com/confpapers/CRPITV49Lu.pdf}
    }
    
    Maher, M. J. & Governatori, G. A semantic decomposition of defeasible logic 1999 Proc. American National Conference on Artificial Intelligence (AAAI-99), pp. 299-305  inproceedings URL  
    Abstract: We investigate defeasible logics using a technique which decomposes the semantics of such logics into two parts: a specification of the structure of defeasible reasoning and a semantics for the meta-language in which the specification is written. We show that Nute's Defeasible Logic corresponds to Kunen's semantics, and develop a defeasible logic from the well-founded semantics of Van Gelder, Ross and Schlipf. We also obtain a new defeasible logic which extends an existing language by modifying the specification of Defeasible Logic. Thus our approach is productive in analysing, comparing and designing defeasible logics.
    BibTeX:
    @inproceedings{aaai99,
      author = {Maher, Michael J. and Governatori, Guido},
      title = {A semantic decomposition of defeasible logic},
      booktitle = {Proc. American National Conference on Artificial Intelligence (AAAI-99)},
      publisher = {AAAI Press},
      year = {1999},
      pages = {299-305},
      url = {http://www.aaai.org/Press/Proceedings/AAAI/1999/aaai1999.html}
    }
    
    Milosevic, Z. & Governatori, G. Guest editors' introduction 2005 International Journal of Cooperative Information Systems
    Vol. 14 (2-3) , pp. 73-76 
    article DOI  
    BibTeX:
    @article{DBLP:journals/ijcis/MilosevicG05,
      author = {Zoran Milosevic and Guido Governatori},
      title = {Guest editors' introduction},
      journal = {International Journal of Cooperative Information Systems},
      year = {2005},
      volume = {14},
      number = {2-3},
      pages = {73-76},
      doi = {http://dx.doi.org/10.1142/S021884300500116X}
    }
    
    Milosevic, Z., Governatori, G. & Bartolini, C. Editorial: Contract architectures and languages 2009 International Journal of Business Process Integration and Management
    Vol. 4 (3) , pp. 151-153 
    article  
    BibTeX:
    @article{ijbpim:ed,
      author = {Milosevic, Zoran and Governatori, Guido and Bartolini, Claudio},
      title = {Editorial: Contract architectures and languages},
      journal = {International Journal of Business Process Integration and Management},
      year = {2009},
      volume = {4},
      number = {3},
      pages = {151-153}
    }
    
    Orgun, M. A., Governatori, G. & Liu, C. Modal Tableaux for Verifying Security Protocols 2006 Formal Approaches to Multi-Agent Systems (FAMAS 2006), pp. 31-46  inproceedings  
    Abstract: To develop theories to specify and reason about various aspects of multi-agent systems, many researchers have proposed the use of modal logics such as belief logics, logics of knowledge, and logics of norms. As multi-agent systems operate in dynamic environments, there is also a need to model the evolution of multi-agent systems through time. In order to introduce a temporal dimension to a belief logic, we combine it with a linear-time temporal logic using a powerful technique called fibring for combining logics. We describe a labelled modal tableaux system for a fibred belief logic (FL) which can be used to automatically verify correctness of inter-agent stream authentication protocols. With the resulting fibred belief logic and its associated modal tableaux, one is able to build theories of trust for the description of, and reasoning about, multi-agent systems operating in dynamic environments.
    BibTeX:
    @inproceedings{OrgGovLiu:famas:06:modal,
      author = {Orgun, Mehmet A. and Governatori, Guido and Liu, Chuchang},
      title = {Modal Tableaux for Verifying Security Protocols},
      booktitle = {Formal Approaches to Multi-Agent Systems (FAMAS 2006)},
      year = {2006},
      pages = {31--46}
    }
    
    Orgun, M. A., Ma, J., Liu, C. & Governatori, G. Analysing Stream Authentication Protocols in Autonomous Agent-Based Systems 2006 2nd IEEE International Symposium on Dependable, Autonomic and Secure Computing (DASC'06), pp. 325-332  inproceedings DOI  
    Abstract: In stream authentication protocols used for large-scale data dissemination in autonomuous systems, authentication is based on the timing of the publication of keys, and depends on trust of the receiver in the sender and belief on whether an intruder can have prior knowledge of a key before it is published by a protocol. Many existing logics and approaches have successfully been applied to specify other types of authentication protocols, but most of them are not appropriate for analysing stream authentication protocols. We therefore consider a fibred modal logic that combines a belief logic with a linear-time temporal logic which can be used to analyse time-varying aspects of certain problems. With this logical system one is able to build theories of trust for analysing stream authentication protocols, which can deal with not only agent beliefs but also the timing properties of an autonomous agent-based system.
    BibTeX:
    @inproceedings{OrgMaLiuGov:DASC:06:analysing,
      author = {Orgun, Mehmet A. and Ma, Ji and Liu, Chuchang and Governatori, Guido},
      title = {Analysing Stream Authentication Protocols in Autonomous Agent-Based Systems},
      booktitle = {2nd IEEE International Symposium on Dependable, Autonomic and Secure Computing (DASC'06)},
      publisher = {IEEE Press},
      year = {2006},
      pages = {325-332},
      doi = {http://dx.doi.org/10.1109/DASC.2006.19}
    }
    
    Padmanabhan, V. & Governatori, G. A Fibred Tableau Calculus for Modal Logics of Agents 2006 Declarative Agent Languages and Technologies IV, pp. 105-122  incollection DOI  
    Abstract: In [15,19] we showed how to combine propositional multimodal logics using Gabbay's fibring methodology. In this paper we extend the above mentioned works by providing a tableau-based proof technique for the combined/ fibred logics. To achieve this end we first make a comparison between two types of tableau proof systems, (graph & path), with the help of a scenario (The Friend's Puzzle). Having done that we show how to uniformly construct a tableau calculus for the combined logic using Governatori's labelled tableau system KEM. We conclude with a discussion on KEM's features.
    BibTeX:
    @incollection{dalt:post,
      author = {Padmanabhan, Vineet and Governatori, Guido},
      title = {A Fibred Tableau Calculus for Modal Logics of Agents},
      booktitle = {Declarative Agent Languages and Technologies IV},
      publisher = {Springer},
      year = {2006},
      pages = {105-122},
      doi = {http://dx.doi.org/10.1007/11961536_8}
    }
    
    Padmanabhan, V. & Governatori, G. On Constructing Fibred Tableaux for BDI Logics 2006 Ninth Pacific Rim International Conference on Artificial Intelligence, pp. 150-160  inproceedings DOI  
    Abstract: In tejelia-02,vineetphd we showed how to combine propositional BDI logics using Gabbay's fibring methodology. In this paper we extend the above mentioned works by providing a tableau-based decision procedure for the combined/fibred logics. We show how to uniformly construct a tableau calculus for the combined logic using Governatori's labelled tableau system KEM
    BibTeX:
    @inproceedings{pricai:06:vineet,
      author = {Padmanabhan, Vineet and Governatori, Guido},
      title = {On Constructing Fibred Tableaux for BDI Logics},
      booktitle = {Ninth Pacific Rim International Conference on Artificial Intelligence},
      publisher = {Springer},
      year = {2006},
      pages = {150-160},
      doi = {http://dx.doi.org/10.1007/11801603_18}
    }
    
    Padmanabhan, V., Governatori, G., Sadiq, S., Colomb, R. M. & Rotolo, A. Process Modelling: The Deontic Way 2006 Conceptual Modelling 2006. Proceedings of the Thirds Asia-Pacific Conference on Conceptual Modelling (APCCM2006), pp. 75-84  inproceedings URL  
    Abstract: Current enterprise systems rely heavily on the modelling and enactment of business processes. One of the key criteria for a business process is to represent not just the behaviours of the participants but also how the contractual relationships among them evolve over the course of an interaction. In this paper we provide a framework in which one can define policies/ business rules using deontic assignments to represent the contractual relationships. To achieve this end we use a combination of deontic/normative concepts like proclamation, directed obligation and direct action to account for a deontic theory of commitment which in turn can be used to model business processes in their organisational settings. In this way we view a business process as a social interaction process for the purpose of doing business. Further, we show how to extend the $i^ast$ framework, a well known organisational modelling technique, so as to accommodate our notion of deontic dependency.
    BibTeX:
    @inproceedings{apccm06,
      author = {Padmanabhan, Vineet and Governatori, Guido and Sadiq, Shazia and Colomb, Robert M. and Rotolo, Antonino},
      title = {Process Modelling: The Deontic Way},
      booktitle = {Conceptual Modelling 2006. Proceedings of the Thirds Asia-Pacific Conference on Conceptual Modelling (APCCM2006)},
      publisher = {Australian Computer Science Communications},
      year = {2006},
      pages = {75-84},
      url = {http://crpit.com/confpapers/CRPITV49Lu.pdf}
    }
    
    Padmanabhan, V., Governatori, G. & Su, K. Knowledge Assessment: A Modal Logic Approach 2007 3rd International Workshop on Knowledge and Reasoning for Answering Questions (KRAQ'07)  inproceedings  
    Abstract: The possible worlds semantics is a fruitful approach used in Artificial Intelligence (AI) for both modelling as well as reasoning about knowledge in agent systems via modal logics. In this work our main idea is not to model/reason about knowledge but to provide a theoretical framework for knowledge assessment (KA) with the help of Monatague-Scott (MS) semantics of modal logic. In KA questions asked and answers collected are the central elements and knowledge notions will be defined from these (i.e., possible states of knowledge of subjects in a population with respect to a field of information).
    BibTeX:
    @inproceedings{kraq:07:surmise,
      author = {Padmanabhan, Vineet and Governatori, Guido and Su, Kaile},
      title = {Knowledge Assessment: A Modal Logic Approach},
      booktitle = {3rd International Workshop on Knowledge and Reasoning for Answering Questions (KRAQ'07)},
      publisher = {ICAI},
      year = {2007}
    }
    
    Padmanabhan, V., Governatori, G. & Thakur, S. Knowledge Assessment: A Modal Logic Approach 2008 PRIMA, pp. 315-322  inproceedings DOI  
    Abstract: The possible worlds semantics is a fruitful approach used in Artificial Intelligence (AI) for both modelling as well as reasoning about knowledge in agent systems via modal logics. In this work our main idea is not to model/reason about knowledge but to provide a theoretical framework for knowledge assessment (KA) with the help of Monatague-Scott (MS) semantics of modal logic. In KA questions asked and answers collected are the central elements and knowledge notions will be defined from these (i.e., possible states of knowledge of subjects in a population with respect to a field of information).
    BibTeX:
    @inproceedings{prima:08:surmise,
      author = {Vineet Padmanabhan and Guido Governatori and Subhasis Thakur},
      title = {Knowledge Assessment: A Modal Logic Approach},
      booktitle = {PRIMA},
      publisher = {Springer},
      year = {2008},
      pages = {315-322},
      doi = {http://dx.doi.org/10.1007/978-3-540-89674-6_35}
    }
    
    Padmanabhan, V. N., Governatori, G. & Sattar, A. Actions Made Explicit in BDI 2001 Advances in Artificial Intelligence, pp. 390-401  inproceedings URL  
    Abstract: The Belief, Desire, Intention (BDI) architecture is increasingly being used in a wide range of complex applications for agents. Many theories and models exists which support this architecture and the recent version is that of Capability being added as an additional construct. In all these models the concept of action is seen in an endogenous manner. We argue that the Result of an action performed by an agent is extremely important when dealing with composite actions and hence the need for an explicit representation of them. The Capability factor is supported using a RES construct and it is shown how the components of a composite action is supported using these two. Further, we introduce an OPP (opportunity) operator which in alliance with Result and Capability provides a better semantics for practical reasoning in BDI.
    BibTeX:
    @inproceedings{vineet1,
      author = {Padmanabhan, Vineet Nair and Governatori, Guido and Sattar, Abdul},
      title = {Actions Made Explicit in BDI},
      booktitle = {Advances in Artificial Intelligence},
      publisher = {Springer-Verlag},
      year = {2001},
      pages = {390-401},
      url = {http://springerlink.metapress.com/index/J4MXPKEXF548QH96}
    }
    
    Pakornpong, P. & Governatori, G. An Optimization for Query Answering on ALC Database 2006 Seventeenth Australasian Database Conference (ADC2006), pp. 129-137  inproceedings URL  
    Abstract: Query answering over OWLs and RDFs on the Semantic Web is, in general, a deductive process. To this end, OWL, a family of web ontology languages based on description logic, has been proposed as the language for the Semantic Web. However, reasoning even on $ALC$, a description logic weaker than OWL, faces efficiency problem. To obviate this problem, at least for $ALC$, we propose a partition approach that improves the efficiency by splitting the search space into independent Aboxes. Each partition class, i.e., an Abox, can be queried independently. The answer to a query is the simple combination of the answers from each Abox. We prove the correctness of this approach and we outline how to represent compactly the content of each independent Abox. This work can be seen as an optimization for querying a deductive semi-structured database.
    BibTeX:
    @inproceedings{adc06stone,
      author = {Pakornpong, Pothipruk and Governatori, Guido},
      title = {An Optimization for Query Answering on ALC Database},
      booktitle = {Seventeenth Australasian Database Conference (ADC2006)},
      publisher = {ACS},
      year = {2006},
      pages = {129-137},
      url = {http://crpit.com/confpapers/CRPITV49Lu.pdf}
    }
    
    Palmirani, M., Governatori, G. & Contissa, G. Temporal Dimensions in Rules Modelling 2010 Legal Knowledge and Information Systems JURIX 2010: The Twenty-Third Annual Conference  inproceedings  
    Abstract: Typically legal reasoning involves multiple temporal dimensions. The contribution of this work is to extend LKIF-rules (LKIF is a proposed mark-up language designed for legal documents and legal knowledge in ESTRELLA Project [3]) with temporal dimensions. We propose an XML-schema to model the various aspects of the temporal dimensions in legal domain, and we discuss the design choices. We illustrate the use of the temporal dimensions in rules with the help of real life examples.
    BibTeX:
    @inproceedings{jurix10dimesnsions,
      author = {Palmirani, Monica and Governatori, Guido and Contissa, Giuseppe},
      title = {Temporal Dimensions in Rules Modelling},
      booktitle = {Legal Knowledge and Information Systems JURIX 2010: The Twenty-Third Annual Conference},
      publisher = {IOS Press},
      year = {2010}
    }
    
    Pham, D. H., Governatori, G. & Raboczi, S. Agents adapt to majority behaviours 2008 The 2008 IEEE International Conference on Research, Innovation and Vision for the Future, 2008. RIVF'08  inproceedings  
    Abstract: Agents within a group can have different perceptions of their working environment and autonomously fulfil their goals. However, they can be aware of beliefs and goals of the group as well as other members so that they can adjust their behaviours accordingly. To model these agents, we explicitly include knowledge commonly shared by the group and that obtained from other agents. By avoiding actions which violate ``mental attitudes'' shared by the majority of the group, agents demonstrate their social commitment to the group. Defeasible logic is chosen as our representation formalism for its computational efficiency, and for its ability to handle incomplete and conflicting information. Hence, our agents can enjoy the low computational cost while performing ``reasoning about others''. Finally, we present the implementation of our multi-agent system.
    BibTeX:
    @inproceedings{rifv08,
      author = {Pham, Duy Hoang and Governatori, Guido and Raboczi, Simon},
      title = {Agents adapt to majority behaviours},
      booktitle = {The 2008 IEEE International Conference on Research, Innovation and Vision for the Future, 2008. RIVF'08},
      publisher = {IEEE},
      year = {2008}
    }
    
    Pham, D. H., Governatori, G., Raboczi, S., Newman, A. & Thakur, S. On Extending RuleML for Modal Defeasible Logic 2008 RuleML 2008: The International RuleML Symposium on Rule Interchange and Applications, pp. 89-103  inproceedings DOI  
    Abstract: In this paper we present a general methodology to extend Defeasible Logic with modal operators. We motivate the reasons for this type of extension and we argue that the extension will allow for a robust knowledge framework in different application areas. The paper presents an extension of RuleML to capture Modal Defeasible Logic.
    BibTeX:
    @inproceedings{ruleml08modal,
      author = {Pham, Duy Hoang and Governatori, Guido and Raboczi, Simon and Newman, Andrew and Thakur, Subhasis},
      title = {On Extending RuleML for Modal Defeasible Logic},
      booktitle = {RuleML 2008: The International RuleML Symposium on Rule Interchange and Applications},
      publisher = {Springer},
      year = {2008},
      pages = {89-103},
      doi = {http://dx.doi.org/10.1007/978-3-540-88808-6}
    }
    
    Pham, D. H., Governatori, G. & Thakur, S. Extended Defeasible Reasoning for Common Goals in n-Person Argumentation Games 2009 Journal of Universal Computer Science
    Vol. 15 (13) , pp. 2653-2675 
    article URL  
    Abstract: Argumentation games have been proved to be a robust and flexible tool to resolve conflicts among agents. An agent can propose its explanation and its goal known as a claim, which can be refuted by other agents. The situation is more complicated when there are more than two agents playing the game.
    We propose a weighting mechanism for competing premises to tackle with conflicts from multiple agents in an n-person game. An agent can defend its proposal by giving a counter-argument to change the "opinion" of the majority of opposing agents. Furthermore, using the extended defeasible reasoning an agent can exploit the knowledge that other agents expose in order to promote and defend its main claim.
    BibTeX:
    @article{jucs09,
      author = {Pham, Duy Hoang and Governatori, Guido and Thakur, Subhasis},
      title = {Extended Defeasible Reasoning for Common Goals in n-Person Argumentation Games},
      journal = {Journal of Universal Computer Science},
      year = {2009},
      volume = {15},
      number = {13},
      pages = {2653--2675},
      url = {http://www.jucs.org/jucs_15_13/extended_defeasible_reasoning_for/jucs_15_13_2653_2675_pham.pdf}
    }
    
    Pham, D. H., Thakur, S. & Governatori, G. Settling on the Group's Goals: An n-Person Argumentation Game Approach 2008 11th Pacific Rim International Conference on Multi-Agents (PRIMA 2008)  inproceedings DOI  
    Abstract: Argumentation games have been proved to be a robust and flexible tool to resolve conflicts among agents. An agent can propose its explanation and its goal known as a claim, which can be refuted by other agents. The situation is more complicated when there are more than two agents playing the game.
    We propose a weighting mechanism for competing premises to tackle with conflicts from multiple agents in an n-person game. An agent can defend its proposal by giving a counter-argument to change the ``opinion'' of the majority of opposing agents. During the game, an agent can exploit the knowledge that other agents expose in order to promote and defend its main claim.
    BibTeX:
    @inproceedings{prima08,
      author = {Pham, Duay Hoang and Thakur, Subhasis and Governatori, Guido},
      title = {Settling on the Group's Goals: An n-Person Argumentation Game Approach},
      booktitle = {11th Pacific Rim International Conference on Multi-Agents (PRIMA 2008)},
      publisher = {Springer},
      year = {2008},
      doi = {http://dx.doi.org/10.1007/978-3-540-89674-6_37}
    }
    
    Pham, D. H., Thakur, S. & Governatori, G. Defeasible Logic to Model n-person Argumentation Game 2008 Twelfth International Workshop on Non-Monotonic Reasoning, pp. 215-222  inproceedings  
    Abstract: In multi-agent systems, an individual agent can pursue its own goals, which may conflict with those hold by other agents. To settle on a common goal for the group of agents, the argumentation/dialogue game provides a robust and flexible tool where an agent can send its explanation for its goal in order to convince other agents. In the setting that the number of agents is greater than two and they are equally trustful, it is not clear how to extend existing argumentation/dialogue frameworks to tackle conflicts from many agents. We propose to use the defeasible logic to model the n-person argumentation game and to use the majority rule as an additional preference mechanism to tackle conflicts between arguments from individual agents.
    BibTeX:
    @inproceedings{nmr08,
      author = {Pham, Duy Hoang and Thakur, Subhasis and Governatori, Guido},
      title = {Defeasible Logic to Model n-person Argumentation Game},
      booktitle = {Twelfth International Workshop on Non-Monotonic Reasoning},
      year = {2008},
      pages = {215-222}
    }
    
    Pothipruk, P. & Governatori, G. A Formal Ontology Reasoning with Individual Optimization: A Realization of the Semantic Web 2005 6th International Conference on Web Information Systems Engineering, pp. 119-132  inproceedings DOI  
    Abstract: Answering a query over a group of RDF data pages is a trivial process. However, in the Semantic Web, there is a need for ontology technology. Consequently, OWL, a family of web ontology languages based on description logic, has been proposed for the Semantic Web. Answering a query over the SemanticWeb is thus not trivial, but a deductive process. However, the reasoning on OWL with data has an efficiency problem. Thus, we introduce optimization techniques for the inference algorithm. This work demonstrates the techniques for instance checking and instance retrieval problems with respect to $ALC$ description logic which covers certain parts of OWL.
    BibTeX:
    @inproceedings{wise05,
      author = {Pakornpong Pothipruk and Guido Governatori},
      title = {A Formal Ontology Reasoning with Individual Optimization: A Realization of the Semantic Web},
      booktitle = {6th International Conference on Web Information Systems Engineering},
      publisher = {Springer},
      year = {2005},
      pages = {119-132},
      doi = {http://dx.doi.org/10.1007/11581062_10}
    }
    
    Pothipruk, P. & Governatori, G. ALE Defeasible Description Logic 2006 19th Australian Joint Conference on Artificial Intelligence, pp. 110-119  inproceedings DOI  
    Abstract: One of Semantic Web strengths is the ability to address incomplete knowledge. However, at present, it cannot handle incomplete knowledge directly. Also, it cannot handle non-monotonic reasoning. In this paper, we extend $ALC^-$ Defeasible Description Logic with existential quantifier, i.e., $ALE$ Defeasible Description Logic. Also, we modify some parts of the logic, resulting in an increasing efficiency in its reasoning.
    BibTeX:
    @inproceedings{DBLP:conf/ausai/PothiprukG06,
      author = {Pakornpong Pothipruk and Guido Governatori},
      title = {ALE Defeasible Description Logic},
      booktitle = {19th Australian Joint Conference on Artificial Intelligence},
      publisher = {Springer},
      year = {2006},
      pages = {110-119},
      doi = {http://dx.doi.org/10.1007/11941439_15}
    }
    
    Riveret, Ré., Governatori, G. & Rotolo, A. Argumentation Semantics for Temporal Defeasible Logic 2006 Third European Starting AI Researcher Symposium (STAIRS 2006), pp. 267-268  inproceedings  
    Abstract: We present an extension of the argumentation semantics for defeasible logic to cover the temporalisation of defeasible logic with permanent and immanent temporal literals
    BibTeX:
    @inproceedings{staris:06:regis,
      author = {Riveret, Régis and Governatori, Guido and Rotolo, Antonino},
      title = {Argumentation Semantics for Temporal Defeasible Logic},
      booktitle = {Third European Starting AI Researcher Symposium (STAIRS 2006)},
      publisher = {IOS Press},
      year = {2006},
      pages = {267-268}
    }
    
    Riveret, Ré., Rotolo, A. & Governatori, G. Interaction between Normative Systems and Cognitive agents in Temporal Modal Defeasible Logic 2007 Normative Multi-agent Systems  inproceedings URL  
    Abstract: While some recent frameworks on cognitive agents addressed the combination of mental attitudes with deontic concepts, they commonly ignore the representation of time. We propose in this paper a variant of Temporal Modal Defeasible Logic to deal in particular with temporal intervals.
    BibTeX:
    @inproceedings{dagstuhl:time,
      author = {Riveret, Régis and Rotolo, Antonino and Governatori, Guido},
      title = {Interaction between Normative Systems and Cognitive agents in Temporal Modal Defeasible Logic},
      booktitle = {Normative Multi-agent Systems},
      publisher = {Internationales Begegnungs- und Forschungszentrum fuer Informatik (IBFI), Schloss Dagstuhl, Germany},
      year = {2007},
      note = {[date of citation: 2007-01-01]},
      url = {http://drops.dagstuhl.de/opus/volltexte/2007/923/pdf/07122.RiveretRegis.Paper.923.pdf}
    }
    
    Roth, B., Riveret, Ré., Rotolo, A. & Governatori, G. Strategic Argumentation: A Game Theoretical Investigation 2007 Proceedings of 11th International Conference on Artificial Intelligence and Law, pp. 81-90  inproceedings DOI  
    Abstract: Argumentation is modelled as a game where the payoffs are measured in terms of the probability that the claimed conclusion is, or is not, defeasibly provable, given a history of arguments that have actually been exchanged, and given the probability of the factual premises. The probability of a conclusion is calculated using a standard variant of Defeasible Logic, in combination with standard probability calculus. It is a new element of the present approach that the exchange of arguments is analysed with game theoretical tools, yielding a prescriptive and to some extent even predictive account of the actual course of play. A brief comparison with existing argument-based dialogue approaches confirms that such a prescriptive account of the actual argumentation has been almost lacking in the approaches proposed so far.
    BibTeX:
    @inproceedings{icail07:game,
      author = {Roth, Bram and Riveret, Régis and Rotolo, Antonino and Governatori, Guido},
      title = {Strategic Argumentation: A Game Theoretical Investigation},
      booktitle = {Proceedings of 11th International Conference on Artificial Intelligence and Law},
      publisher = {ACM Press},
      year = {2007},
      pages = {81-90},
      doi = {http://dx.doi.org/10.1145/1276318.1276333}
    }
    
    Sadiq, S. & Governatori, G. Managing Regulatory Compliance in Business Processes 2010
    Vol. 2 Handbook of Business Process Management, pp. 157-173 
    incollection DOI  
    Abstract: The ever increasing obligations of regulatory compliance are presenting a new breed of challenges for organizations across several industry sectors. Aligning control objectives that stem from regulations and legislation, with business objectives devised for improved business performance, is a foremost challenge. The organizational as well as IT structures for the two classes of objectives are often distinct and potentially in conflict. In this chapter, we present an overarching methodology for aligning business and control objectives. The various phases of the methodology are then used as a basis for discussing state of the art in compliance management. Contributions from research and academia as well as industry solutions are discussed. The chapter concludes with a discussion on the role of BPM as a driver for regulatory compliance and a presentation of open questions and challenges.
    BibTeX:
    @incollection{HandbookBPM:spv,
      author = {Sadiq, Shazia and Governatori, Guido},
      title = {Managing Regulatory Compliance in Business Processes},
      booktitle = {Handbook of Business Process Management},
      publisher = {Springer},
      year = {2010},
      volume = {2},
      pages = {157-173},
      doi = {http://dx.doi.org/10.1007/978-3-642-01982-1_8}
    }
    
    Sadiq, S., Governatori, G. & Naimiri, K. Modelling of Control Objectives for Business Process Compliance 2007 BPM 2007, pp. 149-164  inproceedings DOI  
    Abstract: Business process design is primarily driven by process improvement objectives. However, the role of control objectives stemming from regulations and standards is becoming increasingly important for businesses in light of recent events that led to some of the largest scandals in corporate history. As organizations strive to meet compliance agendas, there is an evident need to provide systematic approaches that assist in the understanding of the interplay between (often conflicting) business and control objectives during business process design. In this paper, our objective is twofold. We will firstly present a research agenda in the space of business process compliance, identifying major technical and organizational challenges. We then tackle a part of the overall problem space, which deals with the effective modeling of control objectives and subsequently their propagation onto business process models. Control objective modeling is proposed through a specialized modal logic based on normative systems theory, and the visualization of control objectives on business process models is achieved procedurally. The proposed approach is demonstrated in the context of a purchase-to-pay scenario.
    BibTeX:
    @inproceedings{SadGovNaim:bpm07,
      author = {Sadiq, Shazia and Governatori, Guido and Naimiri, Kioumars},
      title = {Modelling of Control Objectives for Business Process Compliance},
      booktitle = {BPM 2007},
      publisher = {Springer},
      year = {2007},
      pages = {149-164},
      doi = {http://dx.doi.org/10.1007/978-3-540-75183-0_12}
    }
    
    Skylogiannis, T., Antoniou, G., Bassiliades, N. & Governatori, G. DR-NEGOTIATE - A System for Automated Agent Negotiation with Defeasible Logic-Based Strategies 2005 2005 IEEE International Conference on e-Technology, e-Commerce, and e-Services, pp. 44-49  inproceedings DOI  
    Abstract: This paper reports on a system for automated agent negotiation. It uses the JADE agent framework, and its major distinctive feature is the use of declarative negotiation strategies. The negotiation strategies are expressed in a declarative rules language, defeasible logic and are applied using the implemented defeasible reasoning system DR-DEVICE. The choice of defeasible logic is justified. The overall system architecture is described, and a particular negotiation case is presented in detail.
    BibTeX:
    @inproceedings{eee05,
      author = {Thomas Skylogiannis and Grigoris Antoniou and Nick Bassiliades and Guido Governatori},
      title = {DR-NEGOTIATE - A System for Automated Agent Negotiation with Defeasible Logic-Based Strategies},
      booktitle = {2005 IEEE International Conference on e-Technology, e-Commerce, and e-Services},
      publisher = {IEEE Computer Society},
      year = {2005},
      pages = {44-49},
      doi = {http://dx.doi.org/10.1109/EEE.2005.61}
    }
    
    Skylogiannis, T., Antoniou, G., Bassiliades, N., Governatori, G. & Bikakis, A. DR-NEGOTIATE--- A System for Automated Agent Negotiation with Defeasible Logic-Based Strategies 2007 Data and Knowledge Engineering
    Vol. 63 , pp. 362-380 
    article DOI  
    Abstract: This paper reports on a system for automated agent negotiation, based on a formal and executable approach to capture the behavior of parties involved in a negotiation. It uses the JADE agent framework, and its major distinctive feature is the use of declarative negotiation strategies. The negotiation strategies are expressed in a declarative rules language, defeasible logic, and are applied using the implemented system DR-DEVICE. The key ideas and the overall system architecture are described, and a particular negotiation case is presented in detail.
    BibTeX:
    @article{dke:dr-negotiate,
      author = {Skylogiannis, Thomas and Antoniou, Grigoris and Bassiliades, Nick and Governatori, Guido and Bikakis, Antonis},
      title = {DR-NEGOTIATE--- A System for Automated Agent Negotiation with Defeasible Logic-Based Strategies},
      journal = {Data and Knowledge Engineering},
      year = {2007},
      volume = {63},
      pages = {362-380},
      doi = {http://dx.doi.org/10.1016/j.datak.2007.03.004}
    }
    
    Song, I. & Governatori, G. Nested Rules in Defeasible Logic. 2005 RuleML, pp. 204-208  inproceedings DOI  
    Abstract: Defeasible Logic is a rule-based non-monotonic logic with tractable reasoning services. In this paper we extend Defeasible Logic with nested rules. We consider a new Defeasible Logic, called DL$^ns$, where we allow one level of nested rules. A nested rule is a rule where the antecedent or the consequent of the rule are rules themselves. The inference conditions for DL$^ns$ are based on reflection on the inference structures (rules) of the particular theory at hand. Accordingly DL$^ns$ can be considered an amalgamated reflective system with implicit reflection mechanism. Finally we outline some possible applications of the logic.
    BibTeX:
    @inproceedings{ruleml05insu,
      author = {Insu Song and Guido Governatori},
      title = {Nested Rules in Defeasible Logic.},
      booktitle = {RuleML},
      publisher = {Springer},
      year = {2005},
      pages = {204-208},
      doi = {http://dx.doi.org/10.1007/11580072_18}
    }
    
    Song, I. & Governatori, G. A Compact Argumentation System for Agent System Specification 2006 Third European Starting AI Researcher Symposium (STAIRS 2006), pp. 26-37  inproceedings  
    Abstract: We present a non-monotonic logic tailored for specifying compact autonomous agent systems. The language is a consistent instantiation of a logic based argumentation system extended with Brooks' subsumption concept and varying degree of belief. Particularly, we present a practical implementation of the language by developing a meta-encoding method that translates logical specifications into compact general logic programs. The language allows n-ary predicate literals with the usual first-order term definitions. We show that the space complexity of the resulting general logic program is linear to the size of the original theory
    BibTeX:
    @inproceedings{stairs:06:insu,
      author = {Song, Insu and Governatori, Guido},
      title = {A Compact Argumentation System for Agent System Specification},
      booktitle = {Third European Starting AI Researcher Symposium (STAIRS 2006)},
      publisher = {IOS Press},
      year = {2006},
      pages = {26-37}
    }
    
    Song, I. & Governatori, G. Hardware Implementation of Temporal Nonmonotonic Logics 2006 19th Australian Joint Conference on Artificial Intelligence, pp. 808-817  inproceedings DOI  
    Abstract: In order to apply nonmonotonic logics for specifying industrial automation controllers, we define (1) a method to extend atemporal nonmonotonic logics with temporal operators and (2) a mapping of these new temporal nonmonotonic logics into a Metric Temporal Logic. This mapping provides a formal specification method for real-time temporal reasoning digital circuits for the temporal nonmonotonic logics. We present our method in the context of synthesizing custom digital hardware (called agent chip) automatically from high level agent specifications.
    BibTeX:
    @inproceedings{DBLP:conf/ausai/SongG06,
      author = {Song, Insu and Governatori, Guido},
      title = {Hardware Implementation of Temporal Nonmonotonic Logics},
      booktitle = {19th Australian Joint Conference on Artificial Intelligence},
      publisher = {Springer},
      year = {2006},
      pages = {808-817},
      doi = {http://dx.doi.org/10.1007/11941439_85}
    }
    
    Song, I. & Governatori, G. Designing Agent Chips 2006 5th International Conference on Autonomous Agents and Multi-Agent Systems, pp. 1311-1313  inproceedings DOI  
    Abstract: We outline meta-encoding schemas for compiling nonmonotonic logic theories into Verilog HDL (Hardware Description Language) descriptions. These descriptions can be synthesized into gate level specifications for direct fabrication of silicon chips. The method is applied for designing agent chips incorporating similar features found in the BDI (Belief, Desire, and Intention) and Brooks' subsumption architectures.
    BibTeX:
    @inproceedings{aamas06insu,
      author = {Song, Insu and Governatori, Guido},
      title = {Designing Agent Chips},
      booktitle = {5th International Conference on Autonomous Agents and Multi-Agent Systems},
      publisher = {ACM Press},
      year = {2006},
      pages = {1311-1313},
      doi = {http://dx.doi.org/10.1145/1160633.1160874?}
    }
    
    Song, I. & Governatori, G. Affective Web Service Design 2006 Ninth Pacific Rim International Conference on Artificial Intelligence, pp. 71-80  inproceedings DOI  
    Abstract: In this paper, we propose that, in order to improve customer satisfaction, we need to incorporate communication modes (e.g., speech act) in the current standards of web services specifications. We show that with the communication modes, we can estimate various affects on service consumers during their interactions with web services. With this information, a web-service management system can automatically prevent and compensate potential negative affects, and even take advantage of positive affect
    BibTeX:
    @inproceedings{pricai:06:insu,
      author = {Song, Insu and Governatori, Guido},
      title = {Affective Web Service Design},
      booktitle = {Ninth Pacific Rim International Conference on Artificial Intelligence},
      publisher = {Springer},
      year = {2006},
      pages = {71-80},
      doi = {http://dx.doi.org/10.1007/11801603_10}
    }
    
    Song, I., Governatori, G. & Colomb, R. An Interaction Model for Affect Monitoring 2004 Advances in Artificial Intelligence, pp. 979-984  inproceedings DOI  
    Abstract: This paper investigates how we can precisely define what process designers are ought achieve for what they have promised and more importantly in a way that satisfies human users. Toward these goals, an interaction model for processes and an Affect Monitoring Framework (AMF) are proposed based on our analysis on speech act theory and cognitive-based emotion models. The Affect Monitoring Framework is to detect and predict negative affects on users and to resolve caused or predicted causes of negative affects automatically.
    BibTeX:
    @inproceedings{ai04,
      author = {Song, Insu and Governatori, Guido and Colomb, Robert},
      title = {An Interaction Model for Affect Monitoring},
      booktitle = {Advances in Artificial Intelligence},
      publisher = {Springer-Verlag},
      year = {2004},
      pages = {979-984},
      doi = {http://dx.doi.org/10.1007/b104336}
    }
    
    Song, I., Governatori, G. & Diederich, J. Layered Argumentation for Fuzzy Automation Controllers 2010 Cybernetics and Intelligent Systems (CIS), 2010 IEEE Conference on, pp. 189-194  inproceedings DOI  
    Abstract: We develop a layered argumentation system (LAS) for efficient implementation of Fuzzy automation controllers. LAS extends a logic based proposal of argumentation with subsumption concept and varying degree of confidences in beliefs. We show that this argumentation system can be used to model Fuzzy automation controllers. The argumentation system is based on a nonmonotonic logic, the computational complexity of which is known to be linear to the size of the knowledge base. LAS theories can also be mapped into RTL-VHDL (Register Transfer Level-VLSI Hardware Description Language) or RTL Verilog for very efficient hardware implementation of Fuzzy automation controllers.
    BibTeX:
    @inproceedings{cis-ram:2010,
      author = {Song, Insu and Governatori, Guido and Diederich, Joachim},
      title = {Layered Argumentation for Fuzzy Automation Controllers},
      booktitle = {Cybernetics and Intelligent Systems (CIS), 2010 IEEE Conference on},
      publisher = {IEEE Press},
      year = {2010},
      pages = {189-194},
      doi = {http://dx.doi.org/10.1109/ICCIS.2010.5518559}
    }
    
    Song, I., Governatori, G. & Diederich, J. Automatic Synthesis of Reactive Agents 2010 11th International Conference on Control, Automation, Robotics and Vision, ICARCV 2010  inproceedings  
    Abstract: This paper introduces a new approach to designing smart control chips that enables automatic synthesis of real-time control systems from agent specifications. An agent specification is compiled into a hardware description format, such as RTL-VHDL (Register Transfer Level--VLSI Hardware Description Language) or RTL Verilog, which is synthesized using computer-assisted tools to develop ASIC masks or FPGA configurations. A rule-based specification language called Layered Argumentation System (LAS) is defined and a sound and complete mapping to Verilog is developed. LAS combines fuzzy reasoning and non-monotonic reasoning. This enables chip designers to capture commonsense knowledge and concepts having varying degrees of confidence collaboratively and incrementally.
    BibTeX:
    @inproceedings{song10icarv,
      author = {Song, Insu and Governatori, Guido and Diederich, Joachim},
      title = {Automatic Synthesis of Reactive Agents},
      booktitle = {11th International Conference on Control, Automation, Robotics and Vision, ICARCV 2010},
      publisher = {IEEE Press},
      year = {2010}
    }
    
    Stantic, B., Governatori, G. & Sattar, A. Handling of Current Time in Native XML Databases 2006 Seventeenth Australasian Database Conference (ADC2006), pp. 175-182  inproceedings URL  
    Abstract: The introduction of Native XML databases opens many research questions related to the data models used to represent and manipulate data, including temporal data in XML. Increasing use of XML for Valid Web pages warrants an adequate treatment of now in Native XML databases. In this study, we examined how to represent and manipulate now-relative temporal data. We identify different approaches being used to represent current time in XML temporal databases, and introduce the notion of storing variables such as `now' or `UC' as strings in XML native databases. All approaches are empirically evaluated on a query that time-slices the timeline at the current time. The experimental results indicate that the proposed extension offers several advantages over other approaches: better semantics, less storage space and better response time.
    BibTeX:
    @inproceedings{adc06bela,
      author = {Stantic, Bela and Governatori, Guido and Sattar, Abdul},
      title = {Handling of Current Time in Native XML Databases},
      booktitle = {Seventeenth Australasian Database Conference (ADC2006)},
      publisher = {ACS},
      year = {2006},
      pages = {175-182},
      url = {http://crpit.com/confpapers/CRPITV49Lu.pdf}
    }
    
    Stantic, B., Terenziani, P., Sattar, A., Bottrighi, A. & Governatori, G. Towards an implicit treatment of periodically-repeated medical data 2010
    Vol. 160 MEDINFO 2010. Proceedings of the 13th World Congress on Medical Informatics, pp. 1131-1135 
    inproceedings DOI  
    Abstract: Temporal information plays a crucial role in medicine, so that in Medical Informatics there is an increasing awareness that suitable database approaches are needed to store and support it. Specifically, a great amount of clinical data (e.g., therapeutic data) are periodically repeated. Although an explicit treatment is possible in most cases, it causes severe storage and disk I/O problems. In this paper, we propose an innovative approach to cope with periodic medical data in an implicit way. We propose a new data model, representing periodic data in a compact (implicit) way, which is a consistent extension of TSQL2 consensus approach. Then, we identify some important types of temporal queries, and present query answering algorithms to answer them. We also sketch a temporal relational algebra for our approach. Finally, we show experimentally that our approach outperforms current explicit approaches.
    BibTeX:
    @inproceedings{medinfo2010,
      author = {Stantic, Bela and Terenziani, Paolo and Sattar, Abdul and Bottrighi, Alessio and Governatori, Guido},
      title = {Towards an implicit treatment of periodically-repeated medical data},
      booktitle = {MEDINFO 2010. Proceedings of the 13th World Congress on Medical Informatics},
      publisher = {IOS Press},
      year = {2010},
      volume = {160},
      pages = {1131-1135},
      doi = {http://dx.doi.org/10.3233/978-1-60750-588-4-1131}
    }
    
    Su, K., Sattar, A., Governatori, G. & Chen, Q. A computationally grounded logic of knowledge, belief and certainty. 2005 AAMAS 2005, pp. 149-156  inproceedings DOI  
    Abstract: This paper presents a logic of knowledge, belief and certainty, which allows us to explicitly express the knowledge, belief and certainty of an agent. A computationally grounded model, called interpreted $KBC$ systems, is given for interpreting this logic. The relationships between knowledge, belief and certainty are explored. In particular, certainty entails belief; and to the agent what it is certain of appears to be the knowledge. To formalize those agents that are able to introspect their own belief and certainty, we identify a subclass of interpreted $KBC$ systems, called it introspective $KBC$ systems. We provide sound and complete axiomatizations for the logics. We show that the validity problem for the interpreted $KBC$ systems is PSPACE-complete, and the same problem for introspective $KBC$ systems is co-NP complete, thus no harder than that of the propositional logic.
    BibTeX:
    @inproceedings{aamas05,
      author = {Kaile Su and Abdul Sattar and Guido Governatori and Qingliang Chen},
      title = {A computationally grounded logic of knowledge, belief and certainty.},
      booktitle = {AAMAS 2005},
      publisher = {ACM},
      year = {2005},
      pages = {149-156},
      doi = {http://dx.doi.org/10.1145/1082496}
    }
    
    Su, K., Sattar, A., Wang, K. & Governatori, G. Computationally grounded model of BDI-agents 2005 Proceedings of IJCAI'05, pp. 1581-1582  inproceedings URL  
    Abstract: We introduce a multimodal logic of belief, desire and intention, called OBDI logic, where the changes and computation of agents' beliefs, desires, and desires are based on agents' observations (i.e. local states), and we propose a model checking techniques for the logic based on interpreted systems.
    BibTeX:
    @inproceedings{ijcai,
      author = {Su, Kaile and Sattar, Abdul and Wang, Kewen and Governatori, Guido},
      title = {Computationally grounded model of BDI-agents},
      booktitle = {Proceedings of IJCAI'05},
      publisher = {IJCAI},
      year = {2005},
      pages = {1581-1582},
      url = {http://ijcai.org/papers/post-0148.pdf}
    }
    
    Su, K., Sattar, A., Wang, K., Luo, X., Governatori, G. & Padmanabhan, V. Observation-based Model for BDI-Agents 2005 AAAI 2005, pp. 190-195  inproceedings  
    Abstract: We present a new computational model of BDI-agents, called the observation-based BDI-model. The key point of this BDI-model is to express agents' beliefs, desires and intentions as a set of runs (computing paths), which is exactly a it system in the interpreted system model, a well-known agent model due to Halpern and his colleagues. Our BDI-model is it computationally grounded in that we are able to associate the BDI-agent model with a computer program, and formulas, involving agents' beliefs, desires (goals) and intentions, can be understood as properties of program computations. We present a sound and complete proof system with respect to our BDI-model and explore how symbolic model checking techniques can be applied to model checking BDI-agents. In order to make our BDI-model more flexible and practically realistic, we generalize it so that agents can have multiple sources of beliefs, goals and intentions.
    BibTeX:
    @inproceedings{aaai05,
      author = {Kaile Su and Abdul Sattar and Kewen Wang and Xiangyu Luo and Guido Governatori and Vineet Padmanabhan},
      title = {Observation-based Model for BDI-Agents},
      booktitle = {AAAI 2005},
      publisher = {AAAI Press / The MIT Press},
      year = {2005},
      pages = {190-195}
    }
    
    Thakur, S., Governatori, G., Padmanabhan, V. & Eriksson Lundström, J. Dialogue Games in Defeasible Logic 2007 20th Australian Joint Conference on Artificial Intelligence, AI 2007, pp. 497-506  inproceedings DOI  
    Abstract: In this paper we show how to capture dialogue games in Defeasible Logic. We argue that Defeasible Logic is a natural candidate and general representation formalism to capture dialogue games even with requirements more complex than existing formalisms for this kind of games. We parse the dialogue into defeasible rules with time of the dialogue as time of the rule. As the dialogue evolves we allow an agent to upgrade the strength of unchallenged rules. The proof procedures of tetocl are used to determine the winner of a dialogue game.
    BibTeX:
    @inproceedings{austai07:dialogues,
      author = {Thakur, Subhasis and Governatori, Guido and Padmanabhan, Vineet and Eriksson Lundström, Jenny},
      title = {Dialogue Games in Defeasible Logic},
      booktitle = {20th Australian Joint Conference on Artificial Intelligence, AI 2007},
      publisher = {Springer},
      year = {2007},
      pages = {497-506},
      doi = {http://dx.doi.org/10.1007/978-3-540-76928-6_51}
    }
    
    Wang, M. & Governatori, G. A Framework of Normative-based Contract Management 2007 Formal Methods in Electronic Commerce 2007  inproceedings  
    Abstract: We explore of the feasibility of the computationally oriented institutional agency framework proposed by Governatori and Rotolo testing it against an industrial strength scenario. In particular we show how to encode in defeasible logic the dispute resolution policy described in Article 67 of FIDIC.
    BibTeX:
    @inproceedings{WanGov:fmec07,
      author = {Wang, Miao and Governatori, Guido},
      title = {A Framework of Normative-based Contract Management},
      booktitle = {Formal Methods in Electronic Commerce 2007},
      year = {2007}
    }
    
    Weber, I., Governatori, G. & Hoffmann, Jö. Approximate Compliance Checking for Annotated Process Models 2008 Proceedings of the 1st International Workshop on Governance, Risk and Compliance --- Applications in Information Systems (GRCIS'08), pp. 46-60  inproceedings URL  
    Abstract: We describe a method for validating whether the states reached by a process are compliant with a set of constraints. This serves to (i) check the compliance of a new or altered process against the constraints base, and (ii) check the whole process repository against a changed constraints base, e.g., when new regulations come into being. For these purposes we formalize a particular class of compliance rules as well as annotated process models, the latter by combining a notion from the workflow literature with a notion from the AI actions and change literature. The compliance rules in turn pose restrictions on the desirable states. Each rule takes the form of a clausal constraint, i.e., a disjunction of literals. If for a given state there is a grounded clause none of whose literals are true, then the constraint is violated and indicates non-compliance.
    Checking whether a process is compliant with the rules involves enumerating all reachable states and is in general a hard search problem. Since long waiting times undesirable, it is important to explore restricted classes and approximate methods. We present a polynomial-time algorithm that, for a particular class of processes, computes the sets of literals that are necessarily true at particular points during process execution. Based on this information, we devise two approximate compliance checking methods. One of these is sound but not complete (it guarantees to find only non-compliance instances, but not to find all non-compliance instances); the other method is complete but not sound. We sketch how one can trace the state evolution back to the process activities which caused the (potential) non-compliance, and hence provide the user with some error diagnosis.
    BibTeX:
    @inproceedings{grcis08,
      author = {Weber, Ingo and Governatori, Guido and Hoffmann, Jörg},
      title = {Approximate Compliance Checking for Annotated Process Models},
      booktitle = {Proceedings of the 1st International Workshop on Governance, Risk and Compliance --- Applications in Information Systems (GRCIS'08)},
      publisher = {CEUR Workshop Proceedings},
      year = {2008},
      pages = {46-60},
      url = {http://sunsite.informatik.rwth-aachen.de/Publications/CEUR-WS/Vol-339/paper4.pdf}
    }
    
    RuleML 2008 2008 Rule Representation, Interchange and Reasoning on the Web  proceedings DOI  
    BibTeX:
    @proceedings{RuleML08,,
      title = {RuleML 2008},
      booktitle = {Rule Representation, Interchange and Reasoning on the Web},
      publisher = {Springer},
      year = {2008},
      doi = {http://dx.doi.org/10.1007/978-3-540-88808-6}
    }
    
    Intelligent Agents and Multi-Agent Systems, 11th Pacific Rim International Conference on Multi-Agents, PRIMA 2008, Hanoi, Vietnam, December 15-16, 2008. Proceedings 2008 PRIMA  proceedings  
    BibTeX:
    @proceedings{DBLP:conf/prima/2008,,
      title = {Intelligent Agents and Multi-Agent Systems, 11th Pacific Rim International Conference on Multi-Agents, PRIMA 2008, Hanoi, Vietnam, December 15-16, 2008. Proceedings},
      booktitle = {PRIMA},
      publisher = {Springer},
      year = {2008}
    }
    
    RuleML 2010: 4th International Web Rule Symposium 2010 (6403) Semantic Web Rules - International Symposium, RuleML 2010  proceedings  
    BibTeX:
    @proceedings{ruleml2010,,
      title = {RuleML 2010: 4th International Web Rule Symposium},
      booktitle = {Semantic Web Rules - International Symposium, RuleML 2010},
      publisher = {Springer},
      year = {2010},
      number = {6403}
    }
    
    Computational Logic in Multi-Agent Systems, 11th International Workshop, CLIMA XI 2010
    Vol. 6245 CLIMA XI 
    proceedings DOI  
    BibTeX:
    @proceedings{clima2010,,
      title = {Computational Logic in Multi-Agent Systems, 11th International Workshop, CLIMA XI},
      booktitle = {CLIMA XI},
      publisher = {Springer},
      year = {2010},
      volume = {6245},
      doi = {http://dx.doi.org/10.1007/978-3-642-14977-1}
    }
    
    Agent Computing and Multi-Agent Systems 2009 (5044)   book DOIURL  
    BibTeX:
    @book{prima2007,,
      title = {Agent Computing and Multi-Agent Systems},
      publisher = {Springer},
      year = {2009},
      number = {5044},
      url = {http://www.springer.com/978-3-642-01638-7},
      doi = {http://dx.doi.org/10.1007/978-3-642-01639-4}
    }
    
    Legal Knowledge and Information Systems JURIX 2009: The Twenty-Second Annual Conference 2009 (205)   book URL  
    BibTeX:
    @book{jurix2009,,
      title = {Legal Knowledge and Information Systems JURIX 2009: The Twenty-Second Annual Conference},
      publisher = {IOS Press},
      year = {2009},
      number = {205},
      url = {http://www.iospress.nl/loadtop/load.php?isbn=9781607500827}
    }
    
    Rule Interchange and Applications, International Symposium, RuleML 2009, Las Vegas, Nevada, USA, November 5-7, 2009. Proceedings 2009
    Vol. 5858 RuleML 
    proceedings DOI  
    BibTeX:
    @proceedings{DBLP:conf/ruleml/2009,,
      title = {Rule Interchange and Applications, International Symposium, RuleML 2009, Las Vegas, Nevada, USA, November 5-7, 2009. Proceedings},
      booktitle = {RuleML},
      publisher = {Springer},
      year = {2009},
      volume = {5858},
      doi = {http://dx.doi.org/10.1007/978-3-642-04985-9}
    }
    
    Advances in Modal Logic 2006
    Vol. 6  
    book URL  
    BibTeX:
    @book{govhodven:06:advances,,
      title = {Advances in Modal Logic},
      publisher = {College Press},
      year = {2006},
      volume = {6},
      url = {http://www.aiml.net/volumes/volume6/}
    }
    
    Deontic Logic in Computer Science, 10th International Conference, DEON 2010 2010
    Vol. 6181 DEON 2010 
    proceedings DOI  
    BibTeX:
    @proceedings{deon2010,,
      title = {Deontic Logic in Computer Science, 10th International Conference, DEON 2010},
      booktitle = {DEON 2010},
      publisher = {Springer},
      year = {2010},
      volume = {6181},
      doi = {http://dx.doi.org/10.1007/978-3-642-14183-6}
    }
    
    Proceedings of the 3rd International RuleML-2009 Challenge 2009 (549)   proceedings  
    BibTeX:
    @proceedings{ruleml09-challenge,,
      title = {Proceedings of the 3rd International RuleML-2009 Challenge},
      year = {2009},
      number = {549}
    }
    
    Governatori, G. On the Relationship between Carneades and Defeasible Logic 2011 Procedings of the 13th International Conference on Artificial Intelligence and Law (ICAIL 2011)  inproceedings  
    Abstract: We study the formal relationships between the inferential aspects of Carneades (a general argumentation framework) and Defeasible Logic. The outcome of the investigation is that the current proof standards proposed in the Carneades framework correspond to some variants of Defeasible Logic.
    BibTeX:
    @inproceedings{icail2011carneades,
      author = {Governatori, Guido},
      title = {On the Relationship between Carneades and Defeasible Logic},
      booktitle = {Procedings of the 13th International Conference on Artificial Intelligence and Law (ICAIL 2011)},
      publisher = {ACM Press},
      year = {2011}
    }
    
    Lam, H. & Governatori, G. Towards a model of UAVs Navigation in urban canyon through Defeasible Logic 2011 Journal of Logic and Computation   article  
    Abstract: This paper shows how a non-monotonic rule based system (defeasible logic) can be integrated with numerical computation engines, and how this can be applied to solve the Vehicle Routing Problem (VRP). To this end, we have simulated a physical system from which we can obtain numerical information. The physical system perceives information from its environment and generates predicates that can be reasoned by a defeasible logic engine. The conclusions/decisions derived will then realized by the physical system as it takes actions based on the conclusion derived. Here we consider a scenario where a ``flock'' of UAVs have to navigate within an urban canyon environment. The UAVs are self-autonomous without centralized control. The goal of the UAVs is to navigate to their desired destinations without colliding with each other. In case of possible collision, the UAVs concerned will communicate with each other and use their background knowledge or travel guidelines to resolve the conflicts.
    BibTeX:
    @article{uav,
      author = {Lam, Ho=Pun and Governatori, Guido},
      title = {Towards a model of UAVs Navigation in urban canyon through Defeasible Logic},
      journal = {Journal of Logic and Computation},
      year = {2011}
    }
    
    Lam, H.-P. & Governatori, G. What Are the Necessity Rules in Defeasible Reasoning 2011 11th International Conference on Logic Programming and Nonmonotonic Reasoning (LPNMAR 2011)  inproceedings URL  
    Abstract: This paper investigates a new approach for computing the inference of defeasible logic. The algorithm proposed can substantially reduced the theory size increase due to transformations while preserving the representation properties in different variants of DL. Experiments also show that our algorithm outperform traditional approach by several order of amplitudes.
    BibTeX:
    @inproceedings{lpnmr2011,
      author = {Lam, Ho-Pun and Governatori, Guido},
      title = {What Are the Necessity Rules in Defeasible Reasoning},
      booktitle = {11th International Conference on Logic Programming and Nonmonotonic Reasoning (LPNMAR 2011)},
      publisher = {Springer},
      year = {2011},
      url = {http://www.springerlink.com}
    }
    
    Palmirani, M., Governatori, G. & Giuseppe, C. Modelling Temporal Legal Rules 2011 Procedings of the 13th International Conference on Artificial Intelligence and Law (ICAIL 2011)  inproceedings  
    Abstract: Legal reasoning involves multiple temporal dimensions but the existing state of the art of legal representation languages does not allow us to easily combine expressiveness, performance and legal reasoning requirements. Moreover we also aim at the combination of legal temporal reasoning with the defeasible logic approach, maintaining a computable complexity. The contribution of this work is to extend LKIF-rules with temporal dimensions and defeasible tools, extending our previous work.
    BibTeX:
    @inproceedings{icail2011temporal,
      author = {Palmirani, Monica and Governatori, Guido and Contissa Giuseppe},
      title = {Modelling Temporal Legal Rules},
      booktitle = {Procedings of the 13th International Conference on Artificial Intelligence and Law (ICAIL 2011)},
      publisher = {ACM Press},
      year = {2011}
    }
    

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