Deriving Relationships between Integrity Constraints for Schema Comparison

. Schema comparison is essential for integrating different database schemata. Since the semantics of a schema is also represented by its integrity constraints, they must be considered by a correct schema comparison method. Especially the extensional relationships between classes are determined by the relationship between the corresponding integrity constraint sets. In this paper, we work out the relationships between different types of integrity constraints. As a result, we present rules for comparing integrity constraint sets. These rules can be used after a schema conforming step, where naming, type and structural conflicts are solved, to exactly fix the extensional relationship between object classes. 1 Introduction Schema integration [1] is one of the central issues in logically integrating database systems [6]. Schema integration aims at deriving an integrated schema which is a virtual view on all database classes to be integrated. Traditionally, all existing schema integration m..