The pervasive workflow: a decentralized workflow system supporting long running transactions

Workflow technologies are becoming pervasive in that they enable the execution of business processes in distributed and ubiquitous computing environments. As long running transactions, the execution of workflows in environments without dedicated infrastructures raises transactional requirements due to the dynamicity of resources available to run a workflow instance and the integration of relaxed atomicity constraints at both design and instantiation time. In this paper, we propose an adaptive transactional protocol for the pervasive workflow model developed in a previous work to support the execution of business processes in the pervasive setting. The execution of this protocol takes place in two phases. First candidate business partners are assigned to tasks using an algorithm wherein the selection process is based on both functional and transactional requirements. The workflow execution further proceeds through a hierarchical coordination protocol managed by the workflow initiator and controlled based on a decision table computed as an outcome of the business partner assignment procedure. The resulting workflow execution is compliant with the defined consistency requirements and the coordination decisions depend on the transactional characteristics offered by the partners assigned to each task. An implementation of our theoretical results relying on OWL-S and BPEL technologies is further detailed as a proof of concept