Entity Identi cation in Database Integration

The objective of entity identiication is to determine the correspondence between object instances from more than one database. This paper examines the problem at the instance level assuming that schema level het-erogeneity has been resolved a priori. Soundness and completeness are deened as the desired properties of any entity identiication technique. To achieve sound-ness, a set of identity and distinctness rules are established for entities in the integrated world. We propose the use of extended key, which is the union of keys (and possibly other attributes) from the relations to be matched, and its corresponding identity rule, to determine the equivalence between tuples from relations which may not share any common key. Instance level functional dependencies (ILFD), a form of semantic constraint information about the real-world entities, are used to derive the missing extended key attribute values of a tuple.