Refined termination decision in active databases

Abstract

Termination decision in trigger systems is important to make sure that any rule execution does not result in an infinite loop. In general, it is an undecidable task. Several recent works have been proposed to prove termination under certain situations. However, most of the existing methods only make use of the trigger conditions. The influence of the trigger actions to the trigger conditions is hardly considered. Among the few methods which consider both trigger actions and trigger conditions, they are usually based on some restrictive assumptions, and their trigger architecture may be limited to only certain model. In this paper, we will investigate how the relationship between trigger actions and trigger conditions can be captured in a more general trigger model. We will first introduce the concepts of activator and deactivator. These capture the relationship between the trigger actions of one rule with the trigger condition of another rule. Based on these, we propose a refined method to detect more termination situations than previous works.