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Re: [xml-dev] %x;? - Opportunity for pedantry and exegesis

Tim Bray wrote
> Consider the following content model fragment:
>  %x;?
> as in <!ELEMENT a (%x;?, y)>
> It has been argued to me that this can't possibly
> ever be well-formed per a careful reading of the XML
> spec, and the arguments look correct to me.
> See production [48] and section 4.4.8.
> of course <!ELEMENT a ((%x;)?, y)> works.
> I've been told that the XHTML DTDs would suffer
> if this is true.

The OASIS/Nist conformance suite [1] contains many tests that check (a) PE
token expansion and (b) the grammar checking for content models (with
specific tests for misplaced multiplicity operators), so I think it unlikely
that any of the major XML processors would allow this through.

Our XML Validator [2] is used extensively for XHTML Validation and we have
not received any comments about the DTDs being invalid, so I presume they
are written to avoid this problem.  FYI, here is the error message from
xmlvalid for your example:

--> test.dtd [1:16] : Fatal error: multiplicity specification '?' must
follow immediately after element name or ')'


Rob Lugt
ElCel Technology

[2] http://www.elcel.com/products/xmlvalid.html