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RE: [xml-dev] Most XML vocabularies are too large and inevitably have lots of "holes"

Not sure about the case for schema or instances of it, but with DTDs as the
number of cases a single DTD is made to support, the weaker the support
becomes.  This is a problem for XML where DTDs validate one end of a
production and XSL performs post-validation substitutions.  The DTD cannot
be written tightly enough to ensure the XSL consumes the right tags and
outputs the correct XSL-FO, for example.

We really do lose a lot of time and money to the inability or unwillingness
of providers to create, maintain and provide multiple tight definitions over
singular loose ones.


-----Original Message-----
From: Michael Kay [mailto:mike@saxonica.com] 
Sent: Sunday, December 18, 2011 2:17 PM
To: xml-dev@lists.xml.org
Subject: Re: [xml-dev] Most XML vocabularies are too large and inevitably
have lots of "holes"

Indeed, most standards are too large.

XML is too large. Attributes are unnecessary, mixed content is 
unnecessary, namespaces are unnecessary: without these unnecessary 
concepts, XSD and many other things would have been much simpler.

XSD is certainly too large.

Many application-level standards such as FpML and HL7 are too large.

But stating that something is too large doesn't help to make it smaller. 
(There was a W3C workshop on XSD where everyone agreed it was too big 
but no-one could agree which bits were unnecessary.) There's a basic 
problem that the more people you involve in a design, the larger and 
more complex it becomes. At the extreme, this leads to the failure of 
billion-dollar IT projects. This is a sociological problem in the way 
systems are created. But recognizing the fact doesn't make it go away.

Looking to mathematics for inspiration isn't particularly constructive, 
because IT systems have to fit into the real world, and the real world 
itself suffers from excess complexity; a specification can also fail 
because it oversimplifies, or because it imposes too high a level of 

Michael Kay


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