Ontologies are not the panacea in data integration: A flexible coordinatorto mediate context construction

Shared ontologies describe concepts and relationships to resolve semantic c onflicts amongst users accessing multiple autonomous and heterogeneous info rmation sources. We contend that while ontologies are useful in semantic re conciliation, they do not guarantee correct classification of semantic conf licts, nor do they provide the capability to handle evolving semantics or a mechanism to support a dynamic reconciliation process. Their limitations a re illustrated through a conceptual analysis of several prominent examples used in heterogeneous database systems and in natural language processing. We view semantic reconciliation as a nonmonotonic query-dependent process t hat requires flexible interpretation of query context, and as a mechanism t o coordinate knowledge elicitation while constructing the query context. We propose a system that is based on these characteristics, namely the SCOPES (Semantic Coordinator Over Parallel Exploration Spaces) system. SCOPES tak es advantage of ontologies to constrain exploration of a remote database du ring the incremental discovery and refinement of the context within which a query can be answered. It uses an Assumption-based Truth Maintenance Syste m (ATMS) to manage the multiple plausible contexts which coexist while the semantic reconciliation process is unfolding, and the Dempster-Shafer (DS) theory of belief to model the likelihood of these plausible contexts.