Tacit knowledge is unstructured knowledge that is implicitly present in a community, but is not readily organized or available for its members. Virtual communities can be instrumental in the organization and presentation of such tacit knowledge. In this document we present a platform for the implementation of tailor-made virtual communities, which can be designed and optimized according to the task or the problem involved. Tree examples of multi-user worlds based on this scheme are presented. Springer-Verlag Berlin Heidelberg 2000