RDF (Resource Description Framework) Question:

No. The fundamental model of RDF is independent of XML. RDF is a model describing qualified (or named) relationships between two (Web) resources, or between a Web resource and a literal. At that fundamental level, the only commonality between RDF and the XML World is the usage of the XML Schema datatypes to characterize literals in RDF. In fact, using GRDDL, a way to automate mappings from XML to RDF easily, many XML vocabularies can be considered applications of RDF.Note that one of the serialization formats of RDF is indeed based on XML (RDF/XML), and this is probably the most widely used format today. But others exist, see the separate question on RDF representation