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Duay Hoang Pham, Subhasis Thakur, and Guido Governatori.

Settling on the group's goals: An n-person argumentation game approach. In 11th Pacific Rim International Conference on Multi-Agents (PRIMA 2008), Hanoi, 15-16 Decemebr 2008">Copyrigth © 2008 Springer.
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.
 

Guido Governatori, Duy Hoang Pham, Simon Raboczi, Andrew Newman, and Subhasis Thakur.

On extending {RuleML} for modal defeasible logic. In Nick Bassiliades, Guido Governatori, and Adrian Paschke, editors, RuleML 2008: The International RuleML Symposium on Rule Interchange and Applications, Lecture Notes in Computer Science, Berlin, 2008. Springer, Copyrigth © 2008 Springer.
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.
 

Duy Hoang Pham, Subhasis Thakur, and Guido Governatori.

Defeasible logic to model n-person argumentation game. In Twelfth International Workshop on Non-Monotonic Reasoning, Sydney, 13-15 September 2008.
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.
 

Guido Governatori.

Labelled modal tableaux. In Carlos Areces, Patrick Blackburn, and Rob Goldblatt, editors, Advances in Modal Logic, volume 7. College Publications, London, 2008.
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.
 

Guido Governatori, Jörg Hoffmann, Shazia Sadiq, and Ingo Weber.

Detecting regulatory compliance for business process models through semantic annotations. In 4th International Workshop on Business Process Design, Milan, 1 September 2008 2008.
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.
 

Duy Hoang Pham, Guido Governatori, and Simon Raboczi.

Agents adapt to majority behaviours. In The 2008 IEEE International Conference on Research, Innovation and Vision for the Future, 2008. RIVF'08, IEEE, 2008, Copyrigth © 2008 IEEE.
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.
 

Ingo Weber, Guido Governatori, and Jörg Hoffmann.

Approximate compliance checking for annotated process models. In Marta Indulska, Shazia Sadiq, and Michael zur Muehlen, editors, Proceedings of CAiSE 2008 Workshop on Governance, Risk and Compliance in Information Systems (GRCIS 2008), Montpellier, 17 June 2008.
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.
 

Guido Governatori and Antonino Rotolo.

Changing legal systems: Abrogation and annulment. Part I: Revision of defeasible theories. In Ron van der Meyden and Leon van der Torre, editors, 9th International Conference on Deontic Logic in Computer Science (DEON2008), Lecture Notes in Computer Science. Springer, 2008. Copyrigth © 2008 Springer.
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.
 

Guido Governatori and Antonino Rotolo.

Changing legal systems: Abrogation and annulment. Part II: Temporalised defeasible logic. In Guido Boella, Harko Verhagen, and Muindhar Singh, editors, Proceedings of Normative Multi Agent Systems (NorMAS 2008, Luxembourg 15-16 July 2008.
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 \cite{deon-part1}, of capturing these modification types using belief and base revision.
 

Guido Governatori, Mehmet A. Orgun, and Chuchang Liu.

Modal tableaux for verifying stream authentication protocols. Journal of Autonomous Agents and Multi Agent Systems, 2008., Copyrigth © 2008 Springer.
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.