Web service composition with volatile information

In many Web service composition problems, information may be needed from Web services during the composition process. Existing research on Web service composition (WSC) procedures has generally assumed that this information will not change. We describe two ways to take such WSC procedures and systematically modify them to deal with volatile information. The black-box approach requires no knowledge of the WSC procedure's internals: it places a wrapper around the WSC procedure to deal with volatile information. The gray-box approach requires partial information of those internals, in order to insert coding to perform certain bookkeeping operations. We show theoretically that both approaches work correctly. We present experimental results showing that the WSC procedures produced by the gray-box approach can run much faster than the ones produced by the black-box approach.