Web service composition (WSC) techniques assume that the parameters used to model the environment remain static and accurate throughout the composition's execution. However, WSCs often operate in environments where the parameters of its component services are volatile. To remain optimal, WSCs must adapt to these changes. Adaptation requires up-to-date knowledge about the revised parameters of each of the services. One way of obtaining this knowledge is to query services for their revised parameters. Querying services for their parameters could be time-consuming and expensive. We must therefore carefully manage how queries are conducted. Specifically, an adaptive WSC must know when to query for revised information, and from which service(s) to obtain information. We present a method to selectively query services using the value of changed information (VOC). VOC measures the value of the change that revised information may potentially introduce to the composition. We reduce the comp...