Nested DTDs

Tim Bray tbray at
Fri Jun 18 17:51:55 BST 1999

At 10:30 AM 6/18/99 -0400, Richard L. Goerwitz wrote:
>I'm always wondering why all this "for interoperability" language is
>in the spec.  It's hard to know what weight to assign something that's
>neither legal nor illegal - or something that's technically valid, but
>discouraged in some usage contexts that aren't very clearly defined in
>the spec.

When XML was created, there was no XML software, but there was a considerable
array of existing SGML software.  If you follow all the for-interoperability
rules, your XML docs should work just fine with pre-1996 SGML software.
That's all.  I *think* that's what the spec says:

for interoperability 
      [Definition:] A non-binding recommendation included to increase the 
      chances that XML documents can be processed by the existing installed 
      base of SGML processors which predate the WebSGML Adaptations Annex to 
      ISO 8879. 


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