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BCIT Citations Collection

Belief revision on modal accessibility relations
Proceedings of the 6th International Conference on Agents and Artificial Intelligence in Angers, France, 2014. In order to model the changing beliefs of an agent, one must actually address two distinct issues. First, one must devise a model of static beliefs that accurately captures the appropriate notions of incompleteness and uncertainty. Second, one must define appropriate operations to model the way beliefs are modified in response to different events. Historically, the former is addressed through the use of modal logics and the latter is addressed through belief change operators. However, these two formal approaches are not particularly complementary; the normal representation of belief in a modal logic is not suitable for revision using standard belief change operators. In this paper, we introduce a new modal logic that uses the accessibility relation to encode epistemic entrenchment, and we demonstrate that this logic captures AGM revision. We consider the suitability of our new representation of belief, and we discuss potential advantages to be exploited in future work., Conference paper, Published.
A declarative model for reasoning about form security
Proceedings of the International Conference on Agents and Artificial Intelligence in Lisbon, Portugal 2015. We introduce a formal methodology for analysing the security of digital forms, by representing form signing procedures in a declarative action formalism. In practice, digital forms are represented as XML documents and the security of information is guaranteed through the use of digital signatures. However, the security of a form can be compromised in many different ways. For example, an honest agent might be convinced to make a commitment that they do not wish to make or they may be fooled into believing that another agent has committed to something when they have not. In many cases, these attacks do not require an intruder to break any form of encryption or digital signature; instead, the intruder simply needs to manipulate the way signatures are applied and forms are passed between agents. In this paper, we demonstrate that form signing procedures can actually be seen as a variation of the message passing systems used in connection with cryptographic protocols. We start with an exis ting declarative model for reasoning about cryptographic protocols in the Situation Calculus, and we show how it can be extended to identify security issues related to digital signatures, and form signing procedures. We suggest that our results could be used to help users create secure digital forms, using tools such as IBM’s Lotus Forms software., Conference paper, Published.
Ranking functions for belief change
Proceedings of the 6th International Conference on Agents and Artificial Intelligence in Angers, France, 2014. In this paper, we explore the use of ranking functions in reasoning about belief change. It is well-known that the semantics of belief revision can be defined either through total pre-orders or through ranking functions over states. While both approaches have similar expressive power with respect to single-shot belief revision, we argue that ranking functions provide distinct advantages at both the theoretical level and the practical level, particularly when actions are introduced. We demonstrate that belief revision induces a natural algebra over ranking functions, which treats belief states and observations in the same manner. When we introduce belief progression due to actions, we show that many natural domains can be easily represented with suitable ranking functions. Our formal framework uses ranking functions to represent belief revision and belief progression in a uniform manner; we demonstrate the power of our approach through formal results, as well as a series of natural problems in commonsense reasoning., Conference paper, Published.