Inconsistency management for description logics

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Copyright: Lee, Kevin
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Abstract
Description logics belong to a family of knowledge representation formalisms that are widely used for representing ontologies. However, ontologies are subject to changes and are susceptible to logical errors as they evolve. Ontology reasoners are able to identify these errors, but they provide very limited support for resolving them. In particular, the existing tools do not provide adequate support to prevent logical errors from being introduced into an ontology. In this research, we investigate three different operations that are directly related to the management of logical inconsistencies in ontologies, namely: ontology contraction, integration and debugging. Ontology contraction concerns the removal of information from a set of description logic sentences, where the resulting set of sentences is consistent. Ontology integration is the problem of combining multiple sets of description logic sentences in a consistent manner. Ontology debugging deals with the removal of description logic sentences to restore the consistency of an ontology. In this regard, contraction and integration can be considered as prevention of logical errors, and debugging as cure. We present a construction of contraction for description logics based on the well-known partial meet contraction for belief bases from the area of belief change. We show that this construction produces more refined solutions, and we show that this construction is governed by a refined set of contraction postulates. Moreover, we recast a class of propositional knowledge integration strategies known as adjustments. We show that these strategies cannot be directly used in the description logic setting due to limitations in the expressive power of description logics. We then provide two new adjustment strategies which are appropriate for description logics, and we show that these strategies produce more refined solutions. Furthermore, we study a tableau-based algorithm that identifies the maximally satisfiable subsets (and minimally unsatisfiable subsets) of an ontology. We show that classical blocking do not guarantee completeness in the presence of cyclic definitions, and we provide revised blocking conditions and prove that they preserve both soundness and completeness. Finally, we introduce a diagrammatic approach for debugging ontologies based on Reduced Ordered Binary Decision Diagrams (ROBDDs).
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Author(s)
Lee, Kevin
Supervisor(s)
Foo, Norman
Meyer, Tommie
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Publication Year
2012
Resource Type
Thesis
Degree Type
PhD Doctorate
UNSW Faculty
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