In this chapter, we present the SWiM system, a prototype semantic wiki for collaboratively building, editing, and browsing mathematical knowledge. SWiM is based on the semantic wiki IkeWiki, but replaces the wiki text with OMDoc, a markup format and ontology language for mathematical documents as the underlying knowledge representation format. Our long-term objective is to evolve SWiM into an integrated platform for ontology-based added-value services. As a social semantic work environment, it will facilitate the creation of a shared, public collection of mathematical knowledge (e.g., for education) and serve scientists as a tool for collaborative development of new theories. We discuss the architecture of the SWiM system focusing on its conceptual base, the OMDoc system ontology. In contrast to other semantic wikis, SWiM uses the system ontology to operationalize the fragments and relations of the underlying representation format, not only the domain ontology, that is, the relations between the represented objects themselves. We will present the prototype implementation of the SWiM system and propose its further evolution into a service platform for science and technology.