[Model Aspect] service basics [AtomPub] 
any atompub server exposes a "service document" that describes what the server is exposing. each service document lists a set of "workspaces", which are just a grouping construct for "collections". workspaces have no interaction semantics in atompub, there is no protocol for creating or deleting them; they just exist. each workspace lists a set of "collections", which is by far the most central construct in atompub. a collection can be listed in more than one workspace.