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let me get back to the examples later. I think her paper should give. On Tue, 17 Apr 2001, Marcus Carr wrote: > I didn't get that impression from her conclusions - are you referring > to the paper located at the other end of > ftp://ftp.informatik.uni-freiburg.de/documents/papers/brueggem/habil.ps? > On the contrary, it appears that she contributed her "decision > algorithm for unambiguous expressions" to James Clark for his SGML > parser. Ambiguity in SGML was occasionally inconvenient, but never > more than that. My understanding was that the requirement for > deterministic models was a concession made to those who were writing > parsers at the expense of those who were creating DTDs. It was no big > deal though - you learned to spot where problems might occur and > avoided them. No - this information is based on personal contact with her indirectly over the last few months (I work with someone who has collaborated with her a *lot*) > > I also heard this: XML Schema WG has discussed deterministic content > > models a lot, and they decided to use deterministic content models largely > > for parser simplicity -- which I think is a non-valid reason at this > > point. > > I suppose the working group felt that if this aspect of a processor > was going to be made more complicated in XML than it was in SGML, it > would discourage the writing of processors. Given that there were > (arguably) only ever two nearly complete SGML (James Clark's and > OmniMark) parsers, I tend to agree with them. I think you know that TREX is from James Clark, and I think James Clark strongly believes in non-deterministic content models for ease of use. cheers - murali. PS: The issues are not just expressiveness when you get to document processing, but closure properties are *very* important, and it gets really messy as XML Schema is *not* closed under 99% of the operations that anyone will need. I am not sure whether I should give this, but I think this is a decently prepared report, written largely by my friend, but it is my work also, I think some people might find it useful -- it is available at http://www.cs.ucla.edu/~mani/xml/papers/conferences/WebDB2001/td-main2.ps
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