*Associate Professor, Tecnia Institute of Advanced Studies, New Delhi
**Director, Guru Nanak Khalsa Institute of Technology and Management Studies, Yamuna Nagar
Online published on 15 February, 2014.
Integrity constraints are a key tool for characterizing the well formedness and Semantics of the information contained in databases. In this regard, it is essential that intelligent database management systems provide their users with automatic support to effectively and efficiently maintain the semantic correctness of data with respect to the given integrity constraints. This paper gives an overview of the field of efficient integrity checking and maintenance for relational as well as deductive databases. It covers both theoretical and practical aspects of integrity control, including integrity maintenance via active rules. New lines of research are outlined, particularly with regard to two topics where a strong impact for future developments can be expected: integrity in XML document collections and in distributed databases. Both pose a number of new and highly relevant research challenges to the database community. An approach to database interoperation is proposed here that exploits the semantic information provided by integrity constraints defined on the component databases. Two roles of integrity constraints in database inter- operation are identified. First, a set of integrity constraints describing valid states of the integrated view can be derived from the constraints defined on the underlying databases. An idea about instance-based database interoperation paradigm is also given, where objects rather than classes are the unit of integration. The notions of objectivity and subjectivity are proposed as an indication of whether a constraint is valid beyond the context of a specific database, and demonstrate the impact of these notions. The main strategies are also outlined for integrity maintenances opposed to checking. Some approaches pursue complete prevention of inconsistent states by checking, at an early stage and in a possibly simplified way, whether the update will violate integrity. In others, offensive transactions are executed anyhow, and then integrity is restored via corrective actions, such as rollbacks or repairs. The focus of this paper is on introducing a new paradigm: The Web as the database, and its implications regarding integrity, i.e., the progressive adaptation of database techniques to Web usage
