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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. > Tim, 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 ')' Regards ~Rob Rob Lugt ElCel Technology http://www.elcel.com [1] http://www.oasis-open.org/committees/xml-conformance/xml-test-suite.shtml [2] http://www.elcel.com/products/xmlvalid.html
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