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Beyond Monotonic Inheritance

Novel Approaches for Representing Ontology Data

Semantic Web Services (SWS), the convergence of Semantic Web and Web Services, is the emerging next major generation of the Web, in which e-services and business communication become more knowledge-based and agent-based. In the SWS vision, service descriptions are built partly upon process ontologies widely shared ontological knowledge about business processes which are represented using Semantic Web techniques for declarative knowledge representation (KR), e.g., OWL Description Logic or RuleML Logic Programs.

In this project, we investigate a previously unsolved, crucial problem in representing process ontologies using SW KR: how to represent non-monotonic inheritance reasoning, in which at each (sub)class in the class hierarchy, any inherited property value may be overridden with another value, or simply cancelled (i.e., not inherited). Non-monotonic inheritance is an important, heavily-used feature in pre-SWS process ontologies, e.g., ubiquitous in object-oriented (OO) programming. The advantages of non-monotonicity in inheritance include greater reuse/modularity and easier specification, updating, and merging. We focus in particular on the MIT Process Handbook (PH), a large, influential, and well-used process ontologies repository that is representative in its features for non-monotonic inheritance. W3Cs OWL, the currently dominant SW KR for ontologies, is fundamentally incapable of representing non-monotonicity; so too is First Order Logic. Using instead another form of leading SW KR RuleML we give a new approach that successfully represents the PHs style of non-monotonic inheritance. In this Courteous Inheritance approach, PH ontology knowledge is represented as prioritized default rules expressed in the Courteous Logic Programs (CLP) subset of RuleML.

A prototype of our approach is in progress. We aim to use it to enable SWS exploitation of the forthcoming open-source version of the PH.

Project Participants