Reconciling Inconsistencies Between Package-extended Ontology Modules Jie Bao, and Vasant Honavar Artificial Intelligence Research Laboratory Computer Science Department Iowa State University Ames, IA USA 50010 Email: {baojie, honavar}@cs.iastate.edu December 28, 2005 Abstract Construction of ontologies in specific domains (e.g., molecular biology, electronic commerce), is invariably a collaborative activity that requires incorporation of independently generated ontology fragments or ontology modules, and hence reconciliation of inconsistencies among ontology mod- ules. We investigate an approch to reconciling the inconsistencies among ontologies using defeasible axioms. In this framework, each ontology mod- ule can be viewed as an internally consistent unit (called a package) with well-specified access interfaces. Multiple ontology modules or packages can be combined to obtain larger ontologies. Inconsistencies between on- tology modules are handled using defeasible axioms (an axiom in one package can defeat one or more axioms from other packages), thereby making the resulting composite ontology internally consistent. The re- sulting framework supports collaborative ontology construction as well as integration of preexisting ontologies. 1 Introduction Ontologies that capture assumptions about objects and relationships among objects in specific domains of interest are essential enablers of effective use of independently developed distributed data and knowledge sources, software com- ponents and services in applications that span virtually every area of human activity. Construction of ontologies in specific domains (e.g., molecular biology, electronic commerce), is invariably a collaborative activity that involves direct cooperation among multiple domain experts or ontologists or indirect coopera- tion among ontologists through the reuse of previously published, autonomously developed ontology fragments or ontology modules. Because different experts typically have only partial knowledge of the domain, and because ontologies 1