Active Consistency Enforcement for Repairable Database Transitions

. Integrity Maintenance is considered one of the major application fields of rule triggering systems (RTSs). In the case of a given integrity constraint being violated by a database transition these systems trigger repairing actions. However, it has be shown that for any set of constraints there exist unrepairable transitions, which depend on the closure of the constraint set. This implies that integrity maintenance by RTSs is only possible, if the constraint implication problem is decidable. In this paper we analyze RTSs for repairable transitions under the requirement of effect preservation which leads to the definition of critical trigger paths in associated rule hypergraphs. Such paths must be absent which holds if the underlying set of constraints is stratified , but this notion turns out to be too strong to be also necessary. A sufficient and necessary condition for the absence of critical paths is obtained, if sets of constraints are required to be locally stratified . 1 Introd..