This document is not intended to be the "end-all, be-all" of namespace discussions. For the sake of simplicity, I've left a lot of things out and I'm not talking in all the "right technical terms". If you have a healthy knowledge of namespaces already, you'll probably find something to nitpick about, and that's ok... this document is not definitive but rather an end-level, low-tech bundle of joy.
The Publishing Requirements for Industry Standard Metadata (PRISM) specification defines a standard for interoperable content description, interchange, and reuse in both traditional and electronic publishing contexts. PRISM recommends the use of certain existing standards, such as XML, RDF, the Dublin Core, and various ISO specifications for locations, languages, and date/time formats. Beyond those recommendations, it defines a small number of XML namespaces and controlled vocabularies of values, in order to meet the goals listed above.