A METHODOLOGY FOR INTEGRATION OF HETEROGENEOUS DATABASES

The transformation of existing local databases to meet diverse applica tion needs at the global level is performed through a four-layered pro cedure that stresses total schema integration and virtual integration of local databases. The proposed methodology covers both schema integr ation and database integration, and uses a four-layered schema archite cture (local schemata, local object schemata, global schema, and globa l view schemata) with each layer presenting an integrated view of the concepts that characterize the layer below. Mechanisms for accomplishi ng this objective are presented in theoretical terms, along with a run ning example. Object equivalence classes, property equivalence classes , and other related concepts are discussed in the context of logical i ntegration of heterogeneous schemata, while object instance equivalenc e classes and property instance equivalence classes, and other related concepts are discussed for data integration purposes. The proposed me thodology resolves naming conflicts, scaling conflicts, type conflicts , and level of abstraction, and other types of conflicts during schema integration, and data inconsistencies during data integration.