Abstract
Maintaining the integrity of data is the most critical issues involved in designing in database systems. In relational database systems, there are four common integrity constraints: the key constraint, entity integrity, referential integrity, and semantic integrity. A relational database is commonly considered to have referential integrity if there are no unmatched foreign key values. This chapter discusses attribute referential integrity (ARI), an expanded concept that allows referential integrity to be specified on any attribute of a relation. It also explains the specifications of the new referential integrity constraint on the entity-relationship and relational models. ARI ensures that a value appearing in the referencing attribute of one relation appears in the referenced attribute of the other relation, where these two relations are not necessarily distinct and referencing or referenced attributes can be a combination of multiple attributes. The ARI constraint can be directly represented on the referencing attribute of a relation by specifying a referenced attribute of the other relation.
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