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RE: Schemas and Semantics (was: A Personal Reply...)

• From: Matthew Gertner <matthew.gertner@s...>
• To: 'Gavin Thomas Nicol' <gtn@e...>, xml-dev@l...
• Date: Thu, 15 Mar 2001 11:59:24 +0100

Gavin,

I generally agree with Rick's comments on this. To make this clear, my
answer to your question is a strong no. If element type "foo" has specific
semantics (and it always does IMO), this doesn't mean that these semantics
are obvious from the instance. Some examples:
1) "foo" should be displayed as a long text field when represented in a web
form.
2) The possible values of "foo" are contained in column X of table Y of
database Z.
3) "foo" in schema X maps to "bar" in schema Y.
4) When foo is changed, a mail should be sent to "matthew@s...".
5) "foo" is described in prose as "...whatever...".
6) etc.

All of these things tell us useful information about the meaning of "foo".
None of them can be deduced directly from the instance. BTW: For things like
2) Rick's Schematron is supercool. Combining Schematron with SAF is one of
the most promising approaches to representing formalized semantics that I
have seen, certainly more promising than RDF and the like (more flame bait,
I must be on a roll...).

Another BTW: My question wasn't meant to be facetious or rhetorical.
Obviously there is a strong feeling out there that element types can be
ambiguous. Is there a real-world example of this that I can sink my teeth
into?

Cheers,
Matt

> -----Original Message-----
> From: Gavin Thomas Nicol [mailto:gtn@e...]
> Sent: Thursday, March 15, 2001 3:51 AM
> To: Matthew Gertner; xml-dev@l...
> Subject: RE: Schemas and Semantics (was: A Personal Reply...)
> 
> 
> > a) I still don't believe that there is even one noncontrived 
> > example where an element in an instance truly has ambiguous 
> > semantics. 
> 
> In which case one wouldn't need schemas, right? After all, the
> instance defines the semantics, right?
> 
> 

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