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   Re: [xml-dev] Notations for datatypes

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> Rick Jelliffe reminded me in private email that he had proposed notations 
> to the W3C XML Schema WG as a way of declaring data types. Let me ask a few 
> questions about a notation-based design for declaring datatypes:
> 1. How do you declare the types of attributes?
> 2. How do you define common libraries of data types using notations that 
> are shared across schemas?
> 3. How would using a syntax based on notations simplify the design of the 
> schema language as a whole - what difference would it make?

Well, I think there are many things that answer #3 in favor of notations, but 
there is at least one that I think is extremely obvious and probably would be 
accepted by most viewpoints.

Using notations for data types leaves them within the information layer 
defined strictly by XML 1.0, and thus means they are accessible to most 
generic XML processing tools, including the two most popular: DOM and SAX.  It 
would obviate the pernicious PSVI, and more objectively, remove the need for 
out-of-band mappings of XML information items to additional notations.

Of course, all that having been said, it would continue to be unavailable in 
XPath/XSLT, but then XPath/XSLT 2.0, rather than loading down those languages 
with a despicable level of complexity, could simply add simple DTD construct 
access tools to the library, and thus enable data type processing as well as 
an entire class of other useful constructs that notations enable.

I still don't like the idea of baked-in static/structured type libraries, but 
it would be easier for this mess not to affect me if the notation path were 
taken.  My guess is that the problem with notations for attributes was the 

Uche Ogbuji                                    Fourthought, Inc.
http://uche.ogbuji.net    http://4Suite.org    http://fourthought.com
Apache 2.0 API - http://www-106.ibm.com/developerworks/linux/library/l-apache/
Python&XML column: Tour of Python/XML - http://www.xml.com/pub/a/2002/09/18/py.
Python/Web Services column: xmlrpclib - http://www-106.ibm.com/developerworks/w


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