CLIPS-OWL: A Framework for Providing Object-Oriented Extensional Ontology Queries in A Production Rule Engine G. Meditskos ∗,a , N. Bassiliades a a Department of Informatics, Aristotle University of Thessaloniki, 54124, Greece Abstract In this paper, we define a framework, namely CLIPS-OWL, for enabling the CLIPS production rule engine to represent the extensional results of DL reasoning on OWL ontologies in the form of Object-Oriented (OO) mod- els. The purpose of this transformation is to allow CLIPS to use these OO models as static query models that are able to answer extensional ontology queries directly by the RETE reasoning engine during the development of custom CLIPS production rule programs, without interfacing at runtime the external DL reasoner. In that way, any CLIPS-based application may en- hance its functionality by incorporating ontological knowledge without mod- ifying the architecture of the CLIPS rule engine. CLIPS-OWL has been implemented using the Pellet DL reasoner and the CLIPS Object-Oriented Language (COOL). Key words: production rules, ontologies, object-oriented model, CLIPS, OWL 1. Introduction Data integration and transformation are issues that concern many users that wish to utilize Web data or to combine heterogeneous systems, since data are stored on the Web under different formats and each application can only handle a specific format [1][2][3]. To enable a specific tool to manipulate * Corresponding author Email addresses: gmeditsk@csd.auth.gr (G. Meditskos), nbassili@csd.auth.gr (N. Bassiliades) Preprint submitted to Data and Knowledge Engineering April 20, 2011