Selective Querying for Adapting Hierarchical Web Service Compositions Using Aggregate Volatility

Environments in which Web service compositions (WSC) operate are often dynamic. We address the problem of which service to query for up-to-date information in order to adapt a hierarchical WSC, given that queries are not free. Previously,the value of changed information (VOC) has been proposed to select those services for querying whose revised non-functional information is expected to bring about the most change in the composition. In this paper, we present an approach for utilizing VOC in the context of a WSC composed of services and lower level WSCs, which induces a natural hierarchy over the composition.