For example if the default namespace is the XSD namespace and there is the following

<element name="foo" type="int" ...>

the canonicalization stylesheet will generate

<xs:element name="foo" type="int" ...>

instead of

<xs:element name="foo" type="xs:int" ...>

as required.

See this post for more on this "QName madness":

http://broadcast.oreilly.com/2009/08/converting-xml-schemas-to-sche-1.html