[Model Aspect] collection basics
a collection has a URI where you can start interacting with the collection, at the most basic level you can GET a list of members (http://tools.ietf.org/html/rfc5023#section-10), and very likely this is somehow paginated (http://tools.ietf.org/html/rfc5023#section-10.1). through its listing in a service document, the collection exposes some interaction information, such as which kind of mediatypes it will accept (http://tools.ietf.org/html/rfc5023#section-8.3.4), and how members of the collection might use categories (http://tools.ietf.org/html/rfc5023#section-8.3.6) to be classified.