The information that is made available through the semantic web will be accessed through complex programs (web-services, sensors, etc.) that may interact in sophisticated ways. Composition guided simply by the specifications of programs' inputs and outputs is insufficient to obtain reliable aggregate performance -hence the recognised need for process models to specify the interactions required between programs. These interaction models, however, are traditionally viewed as a consequence of

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... ce composition rather than as the focal point for facilitating composition. We describe an operational system that uses models of interaction as the focus for knowledge exchange. Our implementation adopts a peer to peer architecture, thus making minimal assumptions about centralisation of knowledge sources, discovery and interaction control.