Re: Roundtripability of identity transform

I was thinking more of changing/losing some useful data - I want to
have some confidence that if I batch process a load of xml I won't
lose some significant information that was present in the old data but
not in the new.

The only biggie I can think of is defaulted values - if the DTD
changes and the new data doesn't keep the reference to the DTD then
the new data won't reflect any changes in the defaulted values.

As an aside, from what you've just said, if the DTD expects a
namespace declaration but that namespace is redundant and gets
removed, the document would no longer validate after the identity
transform (if the DTD was generated in the output).