Extensional Assertions and Integrity Constraints in Federated Schemata
||Extensional Assertions and Integrity Constraints in Federated Schemata
||C. Türker, G. Saake
||Information Systems, Vol. 25, No. 8, pp. 503-526
Integrated access to multiple data sources requires
a homogeneous interface provided by a federated schema. Such a
federated schema should correctly reflect the semantics of the
component schemata of which it is composed. Since the semantics of a
database schema is also determined by a set of semantic integrity
constraints, a correct schema integration has to deal with integrity
constraints existing in the different component schemata.
Traditionally, most schema integration approaches solely concentrate
on the structural integration of given database schemata. Local
integrity constraints are often simply neglected. Their relationship
to global extensional assertions, which form the basic integration
constraints, are even ignored completely. In this paper, we discuss
the impact of global extensional assertions and local integrity
constraints on federated schemata. In particular, we point out the
correspondence between local integrity constraints and global
extensional assertions. The knowledge about the correspondences
between the given integrity constraints and extensional assertions can
then be utilized for an augmented schema integration process.
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