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RE: Are people really using Identity constraints specif ied in


xml schema string len
Len,

Don't knock those XML DTDs.  You can only create small relatively simple things
with them - saves people from injurying themselves and others.  

Same reason why you cannot buy automatic assault weapons (but I have mine
back-ordered from Walmart for when the NRA manage to get that repealed!)

It really must be Friday...

DW

Quoting "Bullard, Claude L (Len)" <len.bullard@i...>:

> You have a declarative system that can dynamically 
> determine concepts from contexts?  Or you have a 
> pattern matcher?  Or you have a human making maps?
> A registry is just another way to store apriori 
> agreements plus a map.
> 
> Ummm... I have an RFP in front of me that requires we 
> deliver a DTD.  Some subsumption is not yet complete.
> 
> len
> 
> 
> From: w3c@d... [mailto:w3c@d...]
> 
> Bruce,
> 
> Unfortunately schema was never intended to perform that role!
> 
> Not the least because it has no context driven mechanisms.
> 
> Apart from that - way too many people think it can do this 'magic' because
> it
> has been over sold - well beyond the original requirements the W3C started
> from.
> 
> We started off with a DTD - simple mission to describe the structure
> permutations of an XML instance.  XSD then subsumed that role.  Snag is
> neither
> is able to deliver fully.  It's all to easy to create an XML instance, or
> set
> of instances, that look perfectly reasonable and straightforward that is
> darn
> hard to then describe in schema.
> 
> I'm reminded of the situation in England in the 1500's - when Latin was
> still
> the official legal language of law - but everyone uses English as the
> working
> language. The solution beckons ; -)
> 
> DW.
> 
> Quoting "Cox, Bruce" <Bruce.Cox@U...>:
> 
> > In my world, attorneys speak "business rules" and IT folk speak "data
> > constraints".  Often, their intention and extension are identical.  A
> > really good schema is the membrane where these two sets touch each
> > other, that is, it is equally successful from both points of view.
> > 
> > 
> > Bruce B. Cox
> > SA4XMLT
> > +1-703-306-2606
> > 
> > -----Original Message-----
> > From: Thomas B. Passin [mailto:tpassin@c...] 
> > Sent: Thursday, August 19, 2004 4:59 PM
> > To: xml-dev@l...
> > Subject: Re:  Are people really using Identity constraints
> > specified in XML schema?
> > 
> > Roger L. Costello wrote:
> > 
> > > - The value of the <minimum-age> must be an integer.  This is a 
> > > constraint on the data.  It will not change over time.
> > 
> > Ha! What happens when the government decides that some relevant age is
> > 67.5 years instead of 67?
> > 
> > > Therefore, an XML Schema should simply constrain <minimum-age> to be 
> > > an integer.  Higher level applications should implement the business 
> > > rule that <minimum-age> be further constrained to 16.
> > > 
> > > How would you characterize the distinction between "business rules" 
> > > and "constraints on data"?
> > 
> > A tricky, tricky issue - what is or is not a "business rule".  I suspect
> > that in practice most constraints that are not business rules are in
> > place for supposed programming reasons, or by force of habit.
> > 
> > In one project I work on, we have a data type that is a union of 1) an
> > enumeration of strings, 2) a string that follows a certain regex
> > pattern, and 3) an integer constrained to a certain range.  No, don't
> > bother to ask - it's one of those multi-agency reconciliations.
> > 
> > --
> > Thomas B. Passin
> > Explorer's Guide to the Semantic Web (Manning Books)
> > http://www.manning.com/catalog/view.php?book=passin
> > 
> > 
> > -----------------------------------------------------------------
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> > 
> > The list archives are at http://lists.xml.org/archives/xml-dev/
> > 
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> > 
> > 
> 
> 
> 
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