Modeling and Evaluation of Redesigning Methodologies for Distributed Workflows

Workflow management systems (WFMS) support the modeling and coordinated execution of processes within an organization. To coordinate the execution of the various activities (or tasks) in a workflow, task dependencies are specified among them. Often, the workflow application domains are such that the workflow is a long-running activity and the various tasks that constitute the workflow need to be executed by systems that are distributed and autonomous in nature, possibly owned by different organizations. In such an environment, it is desirable to minimize the number of communications among the distributed sites and minimize the number of tasks that need to wait for the execution of tasks at other sites. In [3], Atluri et al. propose an approach that can automatically redesign a workflow in such a way that it minimizes the number of communications and interference between sites. This approach performs a semantic categorization of task dependencies, and proposes to use for each categorization, a combination of three techniques – split, compensate and substitute. In this paper, we evaluate the efficacy of the split-task approach. Toward this end, we design a distributed workflow model, develop three performance metrics, and evaluate the redesign approach using simulation. The simulation results clearly indicate that the splittask approach significantly reduces the inter-site communication and improves the task concurrency within the workflow.