As Web Service technology becomes popular in organizations, we happen to compose many kinds of Web Services; software components from private UDDIs and programmable Web APIs from portal Websites. Thus we should manage many Web Service compositions to select just practical ones from many candidates. Here is discussed how to do it by task decomposition with task repository and service quality evaluation for many composed Web Service candidates. Our case studies with business trip show us that our system should select practical Web Service compositions from many candidates.