|•||supports user authentication, access rights, and user groups;|
|•||provides various kinds of event summaries that allow to relate contributions of knowledge to the contributing persons, and thus better judge the social relevance of the "knowledge bits";|
|•||allows commenting on concepts and documents in order to exchange assessments in the community;|
|•||employs a weak semantics: semantic constraints are hard to enforce in a distributed user community where the knowledge evolves bottom-up, from pieces, e.g., concepts may be overlapping (in their textual definitions), and relations may be cyclic rather than purely hierarchic;|
|•||provides powerful and composable filtering and sorting criteria, and means to structure the document collections and the whole index of concepts. Concept indexes tend to grow quickly and subindexes are the recommended means of tailoring the knowledge to one's particular interest. Subindexes allow focussing on particular themes, document subsets, "what's new", "what's most popular", or "what's most authoritative".|
In a concept index, any object, conceptualisation, idea, person, place etc. can be a concept. A concept can be verbally expressed in terms of words, phrases, sentences, paragraphs etc., and also by other concepts.
A concept may be expressed by a number of different text pieces. For instance, the concept "agent-based system" can be expressed by, and therefore may