Most online communites actually become collections of discrete subcommunities. This does not imply that navigating subsites is the only way for users to get information from subcommunities.
User profiling provides the foundation for really effective personalization.
Accordingly, we use the user groups data model to represent subcommunities. A site specification is simply a collection of modules that together comprise either an initial template for subsites or the actual definition of a subsite. The modules designated by the specification are installed in the subsite and made available for immediate use. Subsites themselves are also represented as site specifications. The simplest model is to have subsites branch irrevocably from their templates upon creation, so that no changes made to templates are ever propagated to subsites.