Regarding 1:<p>* XML is the most popular vehicle for representing loosely-structured, heirarchical data. Relational databases can't do this very well. ...XML can be mapped straightforwardly to the objects and data structures of modern programming languages, so it works better than relational modeling for serializing things like object graphs.*<p>While his estimate of market share is off (he suggested &#62;50%), he was right about the future popularity of document databases. The only thing he got wrong was the specific serialization format.