Hi,
I've never used Blender, so I'm flying a little blind here, but a
quick search reveals that Collada export is not built in to Blender,
you have to get one of several plugins. I'm guessing that you may be
confusing XML with Collada. Collada is an XML language, but not all
XML is Collada. In fact, some XML is KML, and a host of other
languages and formats.
ManoM