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Re: specify element type depending of same element attribute value?

From: <noah_mendelsohn@us.ibm.com>
Date: Sun, 21 May 2006 16:02:58 -0400
To: Philippe Poulard <Philippe.Poulard@sophia.inria.fr>
Cc: "'Crni Gorac'" <cgorac@gmail.com>, Michael Kay <mike@saxonica.com>, xmlschema-dev@w3.org
Message-ID: <OFCB1284BB.815F3A73-ON85257175.004F89BA-85257175.006E2349@lotus.com>

Thank you for forwarding this.  I've only had the opportunity to take a 
quick look, but it looks like an interesting piece of work.   It's clear 
that finding appropriate means of capturing co-constraints will be very 
valuable to the XML community.  I would be curious for your thoughts on 
the relationship between the desire for powerful constraint checking that 
the issues raised in the TAG finding, "The Rule of Least Power" [1].  It 
seems to me that, to the extent practical, it is desirable to focus on 
constraint languages that are simple and declarative, as I think that such 
approaches will greatly facilitate the development of tools for 
databinding, user interface creation, etc.  I don't think I've reviewed 
your proposal in enough detail to have an informed opinion, but a quick 
skim suggested that it points toward using somewhat more "powerful" 
languages.  These presumably have the advantage that they can effectively 
express more elaborate constraints, but sometimes at the cost of making it 
difficult to easily discover that a particular constraint is in fact a 
straightforward one.   This is a tradeoff that the Schema WG has been 
wrestling with, as there too, some members are inclined torward approaches 
that are more powerful (in the sense of the finding), and some are willing 
to leave behind more difficult use cases in favor of a solution that's 
easier to optimize and easier to reason about.   I'm curious whether you 
have considered such tradeoffs.  Thanks very much.


[1] http://www.w3.org/2001/tag/doc/leastPower 

Noah Mendelsohn 
IBM Corporation
One Rogers Street
Cambridge, MA 02142

Philippe Poulard <Philippe.Poulard@sophia.inria.fr>
05/15/2006 05:41 AM
        To:     noah_mendelsohn@us.ibm.com
        cc:     Michael Kay <mike@saxonica.com>, "'Crni Gorac'" 
<cgorac@gmail.com>, xmlschema-dev@w3.org
        Subject:        Re: specify element type depending of same element 
attribute value?

noah_mendelsohn@us.ibm.com wrote:
> And, adding to Mike's answer, the schema workgroup is devoting a lot of 
> effort to choosing the right features for Schema 1.1 that would allow 
> such co-occurrence constraints to be expressed.  Though I can't 
> commit anything, I would expect to see at least some initial proposals 
> whatever is the next public working draft of the Schema 1.1 
>  Stay tuned.


I'm playing with an alternate schema technology that can build content 
models dynamically, as shown in this example :

Thus, co-occurrence constraints are easy to achieve with the Active 
Schema Language :

Of course, this is still experimental, but it's worth seeing ; there are 
lots of ideas that might interest the schema workgroup.


              (. .)
|      Philippe Poulard       |
        Have the RefleX !
Received on Sunday, 21 May 2006 20:03:17 UTC

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