Abstract Interpretation of Active Rules and its Use in Termination Analysis

The behaviour of rules in an active database system can be difficult to predict, and much work has been devoted to the development of automatic support for reasoning about properties such as confluence and termination. We show how abstract interpretation can provide a generic framework for analysis of active rules. Abstract interpretation is a well-understood, semantics-based method for static analysis. Its advantage, apart from generality, lies in the separation of concerns: Once the underlying semantics has been captured formally, a variety of analyses can be derived, almost for free, as approximations to the semantics. Powerful general theorems enable simple proofs of global correctness and uniform termination of specific analyses. We outline these ideas and show, as an example application, a new method for termination analysis. In terms of precision, the method compares favourably with previous solutions to the problem. This is because the method investigates the flow of data rather than just the syntax of conditions and actions.