Re: [relax-ng] close schema language

[Eric van der Vlist <vdv@dyomedea.com>]

MURATA Makoto wrote:

> Michael Fitzgerald wrote:
> 
> 
>>I was wondering what people think of these comments on closed schema
>>languages on XML-DEV.
>>
> 
> I see some advantages in assertion-based schema languages such as Schematron.  
> But I have always wondered why Rick Jelliffe opposes to other languages.  
> What he calls "closed" is not a hangover from DBMS.  Does he really think 
> DocBook and TEI are such hangovers?  "Closed" content models are sometimes 
> (or often) required.


Schematron is the only language I know where "everything which is not 
forbidden is allowed", the main principle of the other languages being 
rather that "everything which is not allowed is forbidden" which, by 
itself, is "closed".

I think then that the opposition between assertion-based and 
structure-based languages is only a partial explanation of a deepest 
difference between Schematron and the other languages. Partial, because 
it is possible to imagine assertion-based languages where "everything 
which is not allowed is forbidden" but it would seem less natural to 
define structure-based languages where "everything which is not 
forbidden is allowed".

Eric
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