Merging Inheritance Hierarchies for SchemaIntegration based on Concept Lattices 1

Merging inheritance hierarchies is an essential task of schema integration as part of the design of a federated database. Based on the formalization of inheritance hierarchies as concept lattices we present an eecient algorithm for deriving an integrated inheritance hierarchy as result of merging two inheritance hierarchies with overlapping extensions and types. Several methods are presented to modify the integrated hierarchy to optimize the resulting object-oriented schema with respect to certain quality criteria (disjoint specialization , number of classes, support of null values, etc). These methods are necessary to adjust the integrated schema to speciic requirements and for realizing application-speciic views.