The Explorer's Guide to the Semantic Web - Thomas B. Passin Manning Publications ISBN 1932394206
This is a very interesting guide to a great deal of the background to the SemanticWeb. There is a diagram on P.14 which shows the SemanticWebLayerCake, which shows how the SemanticWeb can be considered as a series of layers, starting at the base with a representation layer, often but not necessarily XML (ExtensibleMarkupLanguage). -- JohnFletcher