Multiple Consistency States of Fixed-time Constraints in Grid Workflow Systems

To verify fixed-time constraints in grid workflow systems, the consistency and the inconsistency conditions have been defined in the conventional verification work. However, with a view of the run-time uncertainty of the activity completion duration, we argue that although the conventional consistency condition is fine, the conventional inconsistency condition is too rigorous and covers several different situations. These situations should be handled differently for cost saving while conventionally by the same exception handling. Therefore, in this report, we divide the conventional inconsistency into weak consistency, weak inconsistency and strong inconsistency and treat the conventional consistency as strong consistency. Correspondingly, we develop the verification algorithms for them; and present a method on how to adjust the weak consistency to the strong consistency using the average activity time redundancy and the temporal dependency between the fixed-time constraints; and analyse why the weak inconsistency can be handled by simpler and more economical exception handling. The final comparison and discussion demonstrate that on average our research can achieve better cost effectiveness than the conventional work.