RE: XML within XML - includes, transcludes, whatever

> Wouldn't this idea require two passes through the XML instance to get to
> wellformed *and* valid?  If so, this seems clearly unacceptable
> performance-wise.  Or am I misunderstanding the idea?

One pass is enough: you validate the post-parse form in the
naive (brute-force approach) case, and with a more 
intelligent processor, validate as you parse.