The University of Edinburgh -
Division of Informatics
Forrest Hill & 80 South Bridge

MSc Thesis #92106

Title:Computing Belief Revision
Date: 1992
Abstract:Belief revision is required if a system of beliefs, e.g. a knowledge base, acquires new information which is inconsistent with what is already believed. Human reasoners often do not carefully weigh the evidence for and against a proposition. Instead, they decide to 'believe in one side of the contradiction', beliefs that support the other side become disbelieved. In doing this, some beliefs prove to be more tenacious than others. These are usually convictions that are more central to the reasoner's whole system of beliefs, more useful for his general style of argumentation. This can be thought of as reflecting a preference ordering over beliefs. The focus of this study is how to represent reasoning in a simple explicable way, where conflicts are decided on the basis of such an ordering. Beliefs, reasoning to infer new beliefs and belief revision are represented in a logic-based formalism. When new information arrives and is consistent with what is believed, it is simply added. If it is inconsistent with existing beliefs, a consistent subset of the expanded system of beliefs is determined which is preferred on the basis of the ordering. A program based on this model is included.

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