Dynamic changes to workflow instances of Web services

A Web service is a software system designed to support machine-to-machine interactions over a network by utilizing a known set of standards. Workflows are a common mechanism to orchestrate a collection of Web services to complete a particular task. Web service use and workflow construction are governed by a Community of Interest (COI). It is not uncommon for COIs to change workflows given the creation of new Web services, updates to existing services, or new tasks to incorporate. Current workflow management systems (WFMS) follow a single loop for deployment and monitoring that allows changes to be made only after all instances are executed or aborted. Thus, current commercial WFMS cannot modify a workflow once its execution begins. This is unacceptable in domains where change is frequent and pressing. In this research, we present the design, formal model, and prototype of a novel workflow system that incorporates a second loop to facilitate dynamic change in executing workflow instances comprised of Web services. This double-loop system accommodates dynamic, on-the-fly changes to workflow specifications and migrates these changes to executing instances. An architecture utilizing enhanced inspection and coordination supports the specification of workflow changes and the reconfiguration of executing instances. The system uniquely combines the open-standard workflow language BPEL, a Commercial-off-the-shelf workflow engine, reconfiguration rules, and COI preferences to guide reconfiguration decision making and change management while ensuring system stability.