Increasingly, distributed systems are being constructed by composing a number of components, often legacy applications exposed using Web service interfaces. There are a number of architectural configurations or distribution patterns, which express how such systems are to be deployed. However, the amount of code required to realise these distribution patterns is considerable. Here, we propose a novel Model Driven Architecture using UML 2.0, which takes existing Web service interfaces as its input and generates an executable Web service composition, based on a distribution pattern chosen by the software architect.