Ontologies explicate the contents, essential properties, and relationships between terms in a knowledge base.
Many sources are now accessible with associated ontologies.
Most prior work on the use of ontologies relies on the construction of a single global ontology covering all sources. Such an approach is not scalable and maintainable especially when the sources change frequently. We propose a scalable and easily maintainable approach based on the interoperation of ontologies. To handle user queries crossing the boundaries of the underlying information systems, the interoperation between the ontologies should be precisely de ned. A Graph-Oriented Model for Articulation of Ontology Interdependencies.