A Dynamic Approach to Termination Analysis for Active Database Rules

An important behavioural property for sets of active database rules is that of termination. In current commercial database systems, termination is guaranteed by imposing a xed upper limit on the number of recursive rule rings that may occur. This can have undesirable effects such as prematurely halting correct executions. We describe a new approach based on a dynamic upper limit to the number of rule rings. This limit reeects knowledge about past rule behaviour on the database and provides a more accurate measure for when the DBMS should terminate rule execution. The approach incurs little cost and can easily be integrated with current techniques for static analysis of active rules.