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Joe English wrote:
> But even SGML doesn't require conforming systems to report
> this condition; [4.267] says an ambiguous content model is not
> a "reportable markup error".
>
> (That's probably because nobody knew *how* to detect this condition
> until 1992 when Anne Bruegemann-Klein figured it out, but still...)
Lots of people knew how to detect it, but they all did it differently.
Bruegemann-Klein's great contribution was to provide a rigorous
definition for the condition. (She then went on to show that if a
grammar was deterministic by her definition, a DFA could be built for it
in linear time. That was pretty nice, too.)
> Anyway, AIUI the consensus in the SGML world was that
> the prohibition against ambiguous content models was
> overly restrictive and unnecessary. That W3C XML Schema
> retained the restriction was a big mistake, IMO, one
> that could easily have been avoided by not conflating
> validation with annotation.
You are so right. Look where it got us. XML Schema. Strongly typed XQuery.
Bob Foster
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