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Re: Request to relax PCDATA content model restriction




> I've been corresponding with Terry Allen, who's doing an XMLish version of
> DocBook.  DocBook has a lot of content models like the following:
> 
>   ((%xxx.char.mix;)*)
> 
> where %xxx.char.mix; resolves to (#PCDATA|a|b|c...).  The current XML Lang
> spec doesn't allow for this; production 45 is very specific about how many
> pairs of parens can appear, rather than going for the generalized model
> group solution of productions 40-44.
> 
> Of course, the outermost parens aren't really necessary; you can achieve
> the desired effect with (%xxx.char.mix;)* instead of ((%xxx.char.mix;)*).
> But where content models are heavily parameterized and you can't easily see
> what kind of model you've got, this makes the DTD writer split hairs.
> 
> It should always be safe to throw another couple of paren pairs around a
> model, and currently in XML you can't do this.  Can we consider loosening
> this restriction?

Just a quick note of support for Eve's request. I don't see any advantage
in putting a limit on parens in the first place--if you can match up
two pair, you can match up a hundred pair.

bob