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   RE: [xml-dev] Subtyping in XML

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Every time I read the words Object Oriented or the abbreviation OO in combination with XML, I cringe. Objects aren't XML and XML isn't objects. W3C XML Schema has some features inspired by OO but I wouldn't go as far as calling it OO in XML or even worse calling it an "Object Oriented schema language". 
The core tennets of OO are encapsulation, inheritance and polymorphism. W3C XML Schema gives us 1 of these, once the XQuery REC + F & O are done we'll get another. Encapsulation I doubt we'll ever see given the way the current family of technologies works. 
This is besides the fact that objects are about behavior not data while XML is the exact opposite. 

	-----Original Message----- 
	From: Henry S. Thompson [mailto:ht@cogsci.ed.ac.uk] 
	Sent: Tue 9/10/2002 10:08 AM 
	To: Jeff Lowery 
	Cc: 'paul@prescod.net'; Xml-Dev (E-mail); Dare Obasanjo 
	Subject: Re: [xml-dev] Subtyping in XML

	> That's a bit of a strawman, IMHO.  It may have been the intent of the WG to
	> produce OO in XML
	Not produce, but introduce, and I think you're both a little
	off-target wrt why type definition by restriction and extension are in
	the language.  They're there in large part because the WG had a
	requirement to improve the managability of the process of syntactic
	constraint, by introducing 'inheritance' (read OO-design features)
	into the constraint language.  Think of C --> C++ as a parallel, in so
	far as C++ took a number of OO design patterns generally acknowledged
	to be useful for maintaining large programs over time, which C
	developers had to implement using text-substitution-macros
	(i.e. #include), and moved them into the language.  In introducing the
	tag-type distinction, derivation by restriction and extension, named
	element and attribute groups and substitution groups, the WG was very
	consciously trying to do the same thing, looking at existing 'best
	practise' wrt the use of parameter entities in large DTDs.
	You may or may not think we got it right, but that was the primary
	motivation.  The possibility of a better impedence match between
	documents and application data was a collateral benefit (or not, _ad
	  Henry S. Thompson, HCRC Language Technology Group, University of Edinburgh
	          W3C Fellow 1999--2002, part-time member of W3C Team
	     2 Buccleuch Place, Edinburgh EH8 9LW, SCOTLAND -- (44) 131 650-4440
	            Fax: (44) 131 650-4587, e-mail: ht@cogsci.ed.ac.uk
	                     URL: http://www.ltg.ed.ac.uk/~ht/
	 [mail really from me _always_ has this .sig -- mail without it is forged spam]


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