Re: SV: SV: Schema help

Thank you for your note. 

Bryan Rasmussen wrote:

> I think it would be more interesting to try to figure out a model for 
XSD
> and Schematron to work together

I think the Schematron model does indeed merit a serious look as the 
preferred solution.  I am not yet as expert in it as I would like to be, 
though I do have a general sense of how it works.  I personally have at 
least two concerns that I would want to address before committing to it as 
a solution:

1) Although most widely used schema validators are fairly slow, one can in 
fact implement the XML schema rules at quite high speed.  My team is 
hoping to publish some work in that area in coming months, and I suspect 
that others in the industry are working in the same direction.  I think 
it's important to the success of any technology we choose that it be able 
to meet the performance needs of our customers.  I have a suspicion that 
Schematron, or at least the full Schematron language, may not be as 
optimizable as the rest of XML Schema.   In any case, it's worth some 
quantitative study and some serious architectural analysis before making a 
decision.

2) One important use for XML Schema is in databinding.  Indeed, the W3C 
has been asked by its user community to do some work on facilitating 
databinding based on Schemas.  Though it would be premature for me to draw 
any conclusions, I can imagine reasons why databinding tools might want to 
be aware of co-constraints, and in particular of the relationship between 
those constraints and the particles in content models.  Maybe or maybe not 
that requirement exists and maybe or maybe not Schematron is a good basis 
for meeting it.  That said, I have some intuition that a co-constraint 
system tied a bit more tightly to the existing schema grammars might 
facilitate databinding.

As I say, there's a lot to like about Schematron.  If it's a good 
solution, I think we'll all be glad to support it.  Right now our main 
problem is that the Schema WG has too much important work to do and too 
few people to do it.  I think we're all hoping that co-constraints will 
get some attention in the coming year, but they are not at the moment on 
our list of committed deliverables. 

--------------------------------------
Noah Mendelsohn 
IBM Corporation
One Rogers Street
Cambridge, MA 02142
1-617-693-4036
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Received on Wednesday, 16 November 2005 15:53:22 UTC