Systems check every update to ensure that the database's integrity is never compromised.
The state of the art for expressing semantic constraints, and ensuring integrity with respect to these constraints, has long been richer in academic systems and concept as in deductive databases, however, than what is available in practice in commercial systems. Over the last decade, integrity has only become increasingly important to database users. Databases and their applications are becoming increasingly complex. Databases and database technology is being employed in ever wider and varied contexts. New facilities include triggers, materialized views, object-relational features as definable domains, user defined types and functions, and richer classes of integrity constraints.