III: Small: TROn - Tractable Reasoning with Ontologies

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The Semantic Web is based on describing the meaning ? orsemantics ? of data on the Web by means of metadata ? data describingother data ? in the form of ontologies. The World Wide Web Consortium(W3C) has made several recommended standards for ontology languageswhich differ in expressivity and ease of use. Central to theselanguages is that they come with a formal semantics, expressed inmodel-theoretic terms, which enables access to implicit knowledge byautomated reasoning.Progress in the adoption of reasoning for ontology languages inpractice is currently being made, but several obstacles remain to beovercome for wide adoption on the Web. Two of the central technicalissues are scalability of reasoning algorithms, and dealing withinconsistency of the ontological knowledge bases. These two issuesare being addressed in this project.The scalability issue has its origin in the fact that the expressionof complex knowledge requires sophisticated ontology languages, likethe Web Ontology Language OWL, which are inherently difficult toreason with ? as witnessed by high computational complexities, usuallyExpTime or beyond. This project builds on recent new developments in polynomial time languages around OWL in order to remedy this. In particular, in this project efficient algorithmizations and tools are developed for the largest currently known polynomial-time ontology language, called ELP. Reasoning with knowledge bases with expressivity beyond ELP isenabled through approximating these knowledge bases within ELP.The inconsistency issue has its origin in the fact that large knowledgebases, in particular on the web, are usually not centrally engineered,but arise out of the merging of different knowledge bases withdifferent underlying perspectives and rationales. In this project tools are developed for efficient, i.e., polynomial-time reasoning with inconsistent ontologies.The concrete outcome of the project is an open source reasoningsystem which is able to reason efficiently with (possibly)inconsistent knowledge bases around OWL, in at least an approximatemanner. For further information see the project web page at http://knoesis.wright.edu/faculty/pascal/projects/tron.html