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BCIT Citations Collection
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- An action description language for iterated belief change
- Proceedings of the International Joint Conference on Artificial Intelligence (IJCAI-07), Hyderabad, India, 2007. We are interested in the belief change that occurs due to a sequence of ontic actions and epistemic actions. In order to represent such problems, we extend an existing epistemic action language to allow erroneous initial beliefs. We define a non-Markovian semantics for our action language that explicitly respects the interaction between ontic actions and epistemic actions. Further, we illustrate how to solve epistemic projection problems in our new language by translating action descriptions into extended logic programs. We conclude with some remarks about a prototype implementation of our work., Conference paper, Published.
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- Belief change and cryptographic protocol verification
- Proceedings of the 22nd Conference on Artificial Intelligence (AAAI-07) in Vancouver, BC, July 22–26, 2007. Cryptographic protocols are structured sequences of messages that are used for exchanging information in a hostile environment. Many protocols have epistemic goals: a successful run of the protocol is intended to cause a participant to hold certain beliefs. As such, epistemic logics have been employed for the verification of cryptographic protocols. Although this approach to verification is explicitly concerned with changing beliefs, formal belief change operators have not been incorporated in previous work. In this paper, we introduce a new approach to protocol verification by combining a monotonic logic with a non-monotonic belief change operator. In this context, a protocol participant is able to retract beliefs in response to new information and a protocol participant is able to postulate the most plausible event explaining new information. We illustrate that this kind of reasoning is particularly important when protocol participants have incorrect beliefs., Conference paper, Published.
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- Belief change in the context of fallible actions and observations
- Proceedings of the 21st Conference on Artificial Intelligence (AAAI-06). Boston, MA, July 16–20, 2006. We consider the iterated belief change that occurs following an alternating sequence of actions and observations. At each instant, an agent has some beliefs about the action that occurs as well as beliefs about the resulting state of the world. We represent such problems by a sequence of ranking functions, so an agent assigns a quantitative plausibility value to every action and every state at each point in time. The resulting formalism is able to represent fallible knowledge, erroneous perception, exogenous actions, and failed actions. We illustrate that our framework is a generalization of several existing approaches to belief change, and it appropriately captures the non-elementary interaction between belief update and belief revision., Conference paper, Published.
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- An explicit model of belief change for cryptographic protocol verification
- Proceedings of the 8th International Symposium on Logical Formalizations of Commonsense Reasoning. Stanford, CA, 2007. Cryptographic protocols are structured sequences of messages that are used for exchanging information in a hostile environment. Many protocols have epistemic goals: a successful run of the protocol is intended to cause a participant to hold certain beliefs. As such, epistemic logics have been employed for the verification of cryptographic protocols. Although this approach to verification is explicitly concerned with changing beliefs, formal belief change operators have not been incorporated in previous work. In this preliminary paper, we introduce a new approach to protocol verification by combining a monotonic logic with a non-monotonic belief change operator. In this context, a protocol participant is able to retract beliefs in response to new information and a protocol participant is able to postulate the most plausible event explaining new information. Hence, protocol participants may draw conclusions from received messages in the same manner conclusions are drawn in formalizations of commonsense reasoning. We illustrate that this kind of reasoning is particularly important when protocol participants have incorrect beliefs., Conference paper, Published.
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- Using ranking functions to determine plausible action histories
- Proceedings of the Sixth Workshop on Nonmonotonic Reasoning, Action, and Change (NRAC-05), Edinburgh, Scotland, 2005. We use ranking functions to reason about belief change following an alternating sequence of actions and observations. At each instant, an agent assigns a plausibility value to every action and every state; the most plausible world histories are obtained by minimizing the sum of these values. Since plausibility is given a quantitative rank, an agent is able to compare the plausibility of actions and observations. This allows action occurrences to be postulated or refuted in response to new observations. We demonstrate that our formalism is a generalization of our previous work on the interaction of revision and update., Conference paper, Published.