Multiple states based temporal consistency for dynamic verification of fixed-time constraints in Grid workflow systems

Abstract

To verify fixed-time constraints in Grid workflow systems, consistency and inconsistency conditions have been defined in conventional verification work. However, with a view of the run-time uncertainty of activity completion duration, we argue that, although the conventional consistency condition is feasible, the conventional inconsistency condition is too restrictive and covers several different states. These states, which are handled conventionally by the same exception handling, should be handled differently for the purpose of cost saving. Therefore, in this paper, we divide conventional inconsistency into weak consistency, weak inconsistency and strong inconsistency and treat conventional consistency as strong consistency. Correspondingly, we develop some algorithms on how to verify them. Based on this, for weak consistency we present a method on how to adjust it to strong consistency by using mean activity time redundancy and temporal dependency between fixed-time constraints. For weak inconsistency, we analyse briefly why it can be handled by simpler and more cost-saving exception handling while for strong inconsistency, the conventional exception handling remains deployed. The final quantitative evaluation demonstrates that our research can achieve better cost-effectiveness than the conventional work. Copyright © 2006 John Wiley & Sons, Ltd.