The existing, open Worldwide Web has been successful on a global scale because the cost of participation at a basic level is low and the individual benefit of participation is immediate, rising rapidly as more participants take part. The same cannot currently be said about semantic based systems because the cost of being precise about semantics for sophisticated components is prohibitively high and the cost of ensuring an individual, absolute semantics for a component rises rapidly as more participants take part. OpenKnowledge aims to break out of this deadlock by focusing on semantics related to interaction (which are acquired at low cost during participation) and using this to avoid dependency on a priori semantic agreement; instead making semantic commitments incrementally at run time. The "Open" in OpenKnowledge thus is significant in two senses: it assumes an open system, which anyone may join at any time; it assumes an openness to being joined, achieved through participation at low individual cost.
We shall provide a unifying framework based on interaction models that are mobile in the sense that they may be transferred to other components, this being a mechanism for Web service composition and for coalition formation. A key contribution of OpenKnowledge is to demonstrate that by shifting the emphasis to interaction (the details of which may be hidden from users) we can obtain knowledge sharing of sufficient quality for sustainable communities of practice without the barrier of complex meta-data provision prior to community formation. This requires us to re-interpret forms of contextual reasoning, ontology mapping, query routing and visualisation for this new arena. We ground our research in two testbed areas: bioinformatics and emergency response.