Optimally Distributing Interactions Between Composed Semantic Web Services

When information services are organized to provide some composed functionality, their interactions can be formally represented as workflows. Traditionally, workflows are executed by centralized engines that invoke the necessary services and collect results. If services are clustered (e.g., based on geographic criteria), locally routing intermediary results between services in the same cluster can be more efficient. This paper has several contributions: First, it presents a framework allowing the execution of workflow parts to be mediated by special execution sites. Second, we describe a trigger-based mechanism allowing partial results to be routed between execution sites. Finally, we present an approach for optimally computing the distribution of workflow parts to execution sites accordingly to an integrated cost model for workflow execution. The model is created by merging cost-models provided by individual execution sites trough a Contract Net task brokering protocol. The models consider cost measures for service activation, parameter transfer, and service execution.