Services provide access to software components that can be discovered dynamically via the Internet. The increasing number of services a requesters may be able to use demand support for nding and selecting services. In particular, it is unrealistic to expect that a single service will satisfy complex requirements, so services will have to be combined to match clients' requests. In this paper, we propose a visual, incremental approach for the composition of services, in which we describe the requirements of a requester as a goal which is matched against multiple provider oers. After every match with an oer we decompose the goal into satised and remainder parts. We iterate the decomposition until the goal is satised or we run out of oers, leading to a resolution-like matching strategy. Finally, the individual oers can be composed into a single combined oer and shown to the requester for feedback. Our approach is based on visual specications of pre- and postconditions by graph tra...