Layers, again (was Re: fixing (just) namespaces and validation)

Simon St.Laurent simonstl at
Thu Sep 9 01:59:45 BST 1999

At 05:30 PM 9/8/99 -0400, David Megginson wrote:
>> >There was no warning, however, that DTD syntax might change.
>> I think you're overestimating the syntax changes being described.
>>[...PIs, not syntax changes]
>My fault: I didn't realise that your proposed changes used only PIs.
>I'm not sure that I see how the documents could still be valid from
>the XML 1.0 perspective, though, and if not, the new documents would
>still be backwards incompatible with some (many?) existing XML 1.0

I'm not sure I'm quite off the hook yet.  While the PI approach is nice
because it doesn't have many side effects (it's easily ignored), I'm still
trying to figure out if the processing shift might produce odd results in
some situations.  I think that most of the time, it'll be okay, but I'm
still hunting for lurking weirdness.

My _hope_ is that it'll be 100% backwards compatible with XML 1.0 DTD
validation if the prefixes don't change, and that it'll let through the
cases where the prefix changed but nothing else did.  In that sense, it'd
be incompatible - documents with good namespace matches would still spit
out from validating XML 1.0 processors.  That doesn't seem any worse than
the current situation, but it's worth more thought.

Simon St.Laurent
XML: A Primer (2nd Ed - September)
Building XML Applications
Inside XML DTDs: Scientific and Technical
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