Consistency enforcement in Entity-Relationship and object-oriented models

摘要

Integrity Maintenance is considered one of the major application fields of rule triggering systems (RTSs). Whenever a given integrity constraint is violated by a database transaction, these systems trigger repairing actions. It is shown that for any set of constraints there exist non-repairable transactions, which depend on the closure of the constraint set. Even if non-repairable transactions are excluded, this does not restrain the RTS from producing undesired behaviour. Analyzing this undesired behaviour of RTSs leads to the definition of critical paths in associated rule hypergraphs. Then it is required that such paths are absent. It is shown that this requirement can be satisfied if the underlying set of constraints is stratified. This is always the case for the structural constraints in Entity-Relationship and simple object-oriented models. Moreover, in both cases there is no ambiguity for the selection of rules.