Selective Querying for Adapting Hierarchical Web Service Compositions Figure 6. Recursively update the transition prob- abilities and policies in the hierarchical composi- tion using the revised information WS. Then, we present experimental results on the performance of the adaptive WSC. The results were compared to approaches that use a static, unchanging policy, query random WSs and other heuristics. Architecture The algorithm described in Figure 4 is imple- mented as a WS-BPEL (BPEL Specification, 2005) flow and all WSs were implemented using WSDL (WSDL Specification, 2001). Collect Insurance and Tax Information WS. The algorithm will call findWS*, which would be called again for both the Collect Insurance Infor- mation and Collect Tax and Lien Information WSs. UpdateModel recurses analagously, but also requires the formation of T c (Line 4 in Figure 6) BPEL Implementation of Mortgage Acquisition Process To the WS-BPEL flow, we give the optimal policy, * , of the top level WSC, the start state, and horizon as input. Our experiments utilized the ActiveBPEL engine for executing the BPEL