Component-Based Composition of Wide-Area Workflows

The evolution of workflow models has been characterized by profound flux ever since the formative days of flow charts. Despite, or because of, a proliferation of workflow-oriented standards, none can honestly claim to be ubiquitous. In a widely distributed grid, gaps will inevitably exist in the model of workflows deployed therein. Thus, there is a need to present a consistent view of disparate processes to high-level roles such as analysts. To that end, we propose virtualizing the workflow layer to reconcile such gaps, both in the modeling and the execution sense. Given a wide area network of workflow providers, we overlay it with one based on WS-BPEL, our reference model. For every provider, we build virtualization-enabling silos, realized as components driven by a SCA container. Further, we describe design patterns to facilitate bindings to other models at various levels. Finally, we take reality checks by identifying those patterns in such standards as BPMN, XPDL, WWF and ebBP.