Re: Are we losing out because of grammars?

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

Marcus Carr wrote:
> 
> Eric van der Vlist wrote:
> 
> > Looks like we are going towards 4 different types of XML "schema"
> > languages to define:
> >
> > - The structure
> > - The datatypes
> > - The rules
> > - The semantic.
> 
> This is very interesting - I wonder if we might be heading for another split
> such as the one that saw XSL split into T and FO? The differences are
> becoming more pronounced, and the term "schema language" is starting to lack
> definition as a result.

Yes, and this might be explaining why a "general" schema language is so
difficult to define.

> Eric (or anyone else), how do you differentiate between rules and semantics?

These items would need, for sure, a detailed definition and there are
overlaps.

It is especially true about rules that are a technique and I should
maybe not have mixed it with other items are goals.

I don't think it would be very practical to design a vocabulary using
only rules since there are many of them to write even for a simple
structure and if you forget one of them you get a flaw in your
validation check.

On the other hand, rule based tools are much more flexible than
datatypes or structure schema languages.

Using them together would allow to keep the best of both and should be
possible "both ways":

1) Use this schema and check these rules
but also
2) if this rule is true then use this schema

A set of useful rules would be constraints involving several nodes. A
good example is the unique/key/keyref feature of (current) W3C XML
Schema thats looks so much like something independant of all the other
features.

(They can be compared to the referential constraints added to SQL.)

Semantic being rather a qualification of the "meaning" of the different
nodes.
 
Eric
> --
> Regards,
> 
> Marcus Carr                      email:  mrc@allette.com.au
> ___________________________________________________________________
> Allette Systems (Australia)      www:    http://www.allette.com.au
> ___________________________________________________________________
> "Everything should be made as simple as possible, but not simpler."
>        - Einstein

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Eric van der Vlist       Dyomedea                    http://dyomedea.com
http://xmlfr.org         http://4xt.org              http://ducotede.com
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