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[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] RE: Subtyping in XML
 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@c...] Sent: Tue 9/10/2002 10:08 AM To: Jeff Lowery Cc: 'paul@p...'; Xml-Dev (E-mail); Dare Obasanjo Subject: Re: 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 lib._). ht -- 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@c... 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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