A given database state satisfies integrity if each integrity constraint in the database schema is satisfied. A constraint in prenex normal form is satisfied if, when posed as a query, it returns the answer yes. A constraint in denial form is satisfied if, when posed as a query, it returns the answer no.
Published in Chapter:
Inconsistency-Tolerant Integrity Checking
Hendrik Decker (Instituto Technológico de Informática & Ciudad Politécnica de la Innovación, Spain) and Davide Martinenghi (Politecnico di Milano, Italy)
Copyright: © 2009
|Pages: 10
DOI: 10.4018/978-1-60566-242-8.ch038
Abstract
Integrity checking has been a perennial topic in almost all database conferences, journals, and research labs. The importance of the issue is testified by very large amounts of research activities and publications. They are motivated by the fact that integrity checking is practically unfeasible for significant amounts of stored data without a dedicated approach to optimize the process. Basic early approaches have been extended to deductive, object-relational, XML- (extensible markup language) based, distributed, and other kinds of advanced database technology. However, the fundamental ideas that are already present in the seminal paper (Nicolas, 1982) have not changed much. The basic principle is that, in most cases, a so-called simplification, that is, a simplified form of the set of integrity constraints imposed on the database, can be obtained from a given update (or just an update schema) and the current state of the database (or just the database schema). Thus, integrity, which is supposed to be an invariant of all possible database states, is checked upon each update request, which in turn is authorized only if the check of the simplification yields that integrity is not violated. Here, simplified essentially means more efficiently evaluated at update time. A general overview of the field of simplified integrity checking is provided in Martinenghi, Christiansen, and Decker (2006).