Abstract

We present a state-oriented extension to Datalog called Statelog which comprises two kinds of rules within a simple, yet flexible unified framework, i.e. (i) passive query rules used to express queries and static integrity constraints, and (ii) active transition rules for defining state-changing operations. We show that Statelog is powerful enough to capture many typical active rule applications (including complex updates, integrity enforcement and incremental view maintenance strategies) while retaining a declarative, set-oriented, and deterministic semantics thus reconciling active and deductive databases. Using the Statelog framework, formal results on termination, expressiveness and complexity of active rules are established which carry over to related state-oriented languages like XY-stratified Datalog. We prove that it is undecidable for general Statelog programs whether a program terminates on all databases. We then develop syntactic criteria which guarantee program t...

Citations