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John Cowan <firstname.lastname@example.org> writes:
> ISO/IEC 19757-9 is currently an empty hole titled "Datatype- and
> namespace-aware DTDs". This is a ragbag of ideas to fill that hole.
> 8) Restore multiple element and attribute names separated by |s.
> This makes for conciseness and easy authoring. These constructs were
> dumped in XML DTDs because they imposed extra cost on validating parsers,
> but in this model validation is something done outside parsing, so higher
> cost is worthwhile.
Must be my lack of SGML experience. Can you elaborate on this one?
> General issue: Should there be some way to indicate candidate roots?
> In existing DTDs, any element can be a root.
On a tangent, I'd like to point out that the name of the root element
in the doctypedecl (production 28 in XML, "<!DOCTYPE foo...") is only
required for SGML compatibility and is superfluous in XML where tags
may not be omitted and the first encountered element is unambiguously
the root. If the proposal will break SGML compatibility anyway (the
snipped text suggests it will), it might as well drop this unnecessary
requirement and its associated validity constraint.
Another feature I'd like to see reintroduced is comments inside markup
declarations, they make DTDs so much more readable:
<!ATTLIST foo bar CDATA #REQUIRED -- comment for bar --
baz ID #IMPLIED -- comment for baz -->