Tim Berners-Lee envisions information on the Web being given well-defined meaning, creating the Semantic Web, which would then enable user-interface agents to assist with complex, multi-step, context-dependent tasks, such as arranging travel, appointments, and online purchases. Such agents are assumed to achieve their tasks by composing Web services that perform the functions of individual steps. However, to date, much of the work on the Semantic Web has concerned how to describe and represent the individual services and resources, and not what the agents do to compose them. To avoid hard-coding each task the user wishes to perform, we must give the agent the ability to dynamically compose Web Services according to what will satisfy the user's goals. We are using a large common-sense knowledge base to allow user interface agents to anticipate user goals and flexibly connect them with Web services that can accomplish those goals.