Referential Actions: From Logical Semantics to Implementation

Referential actions rac s are specialized triggers used to au tomatically maintain referential integrity While their local e ects can be grasped easily it is far from obvious what the global semantics of a set RA of interacting rac s should be To capture the intended meaning of RA we rst present an abstract non constructive semantics By formal izing RA as a logic program PRA a constructive semantics is obtained The equivalence of the logic programming semantics and the abstract semantics is proven using a game theoretic characterization which pro vides additional insight into the meaning of rac s As shown in previous work for general rac s it may be infeasible to compute all maximal ad missible solutions Therefore we focus on a tractable subset i e rac s without modi cations We show that in this case a unique maximal ad missible solution exists and derive a ptime algorithm for computing this solution In case a set U of user requests is not admissible a maximal admissible subset of U is suggested