UML is not just for programming. I've had great success with using UML to help students solve complex word problems and to visualize cause and effect. UML enables problem solving, as do online communities. They belong together, as some of the new UML tools demonstrate with their group ware tools for design issues for business processes, coding, business rules etc.
The Uniform Modeling Language is a graphical language tool used for describing complex behaviors and structures for any type of domain, not just programming. It can be used to describe steps for following rules for online communities, for example. And UML offers a standard for a graphical representation of data which leads to more performant group ware, which itself is a type of online community issue.
UML and Wiki belong together...IMHO. ;) I welcome your comments. -- DennisDaniels
See also the Wiki:VisualTour which shows a diagram (not UML as far as I can tell) of the "largest pages reachable in a few clicks".