Motivated by a recent question on the meaning of all sorts of W* acronyms, I would like to to get more information about the Wolfram Data Framework (WDF). On its web page http://www.wolfram.com/data-framework/ it says:

"WDF is a human-readable plaintext format that can be rendered in JSON, XML and other forms."

While the specifications of XML and JSON are well known and documented, I do not know about the specifications of WDF. How does it differ from XML or JSON, what are its advantages above other data specification formats?

If I read e.g. an XML file into Mathematica I get a SymbolicXML expression. Does this have anything to to with WDF?

Can anyone enlighten me?