Termination Analysis of Active Database Rules - Techniques for Increased Precision

An active database consists of a traditional database supplemented by a set of Event-Condition-Action (ECA) rules which automatically evaluate conditions and perform actions in response to events. One of the principal behavioural questions for active database designers is that of termination i.e. is it possible that the ECA rules may trigger each other indefinitely ? In this paper, we examine this problem with the aim of categorising previous work and proposing new techniques to improve the precision of termination analysis. We capture the execution semantics of a set of ECA rules by means of a `while' program, from which we derive a recursion equation for each relation appearing in the program. We then show how unfolding of these recursion equations, satisfiability testing, and interval approximation of the contents of relations can be used to provide a more detailed analysis of termination than achieved by previously proposed techniques. 1 Introduction Active databases provide the f..