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[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] RE: Subtyping in XML
 I'm not sure what definition of encapsulation you are using. Encapsulation in OO is the seperation of an object's interface from it's internal data structures and implementation. All XML documents have is internal structure which have to be exposed to do anything with them. -----Original Message----- From: Maciejewski, Thomas [mailto:Thomas.Maciejewski@l...] Sent: Tue 9/10/2002 10:37 AM To: Dare Obasanjo; Henry S. Thompson; Jeff Lowery Cc: paul@p...; Xml-Dev (E-mail) Subject: RE: Subtyping in XML I think this may be because there seems to be a trend towards using XML in parallel with OO systems. ( serializing objects or to help bridge a relational data base and an objects ) As far as the Inheritance, Encapsulation, polymorphism argument : Inheritance - it has it Encapsulation - I think at least some elements are there polymorphism - I guess your point here is that there is no action so how could there be polymorphism ... but since there is a lack of action then maybe the polymorphism part of this definition is irrelevant? I definitely see XML at least aiding a good OO design ... picture a system of xml data that gets passed around a system of "strategy design pattern" type code that excepts this data in and is able to process what is needed and pass these "objects" on to something else. Doesn't soap also push towards this paradigm? and why would this not be OO or at least a part of the OO paradigm? While it may be arguable that XML is NOT OO I wouldn't get too upset when you hear OO in combination with XML unless you would like to see XML limited to non OO systems. In my opinion it this would be a major limitation. -----Original Message----- From: Dare Obasanjo [mailto:dareo@m...] Sent: Tuesday, September 10, 2002 1:20 PM To: Henry S. Thompson; Jeff Lowery Cc: paul@p...; Xml-Dev (E-mail) Subject: 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] ------------------------------------------------------------------------------ This message is intended only for the personal and confidential use of the designated recipient(s) named above. If you are not the intended recipient of this message you are hereby notified that any review, dissemination, distribution or copying of this message is strictly prohibited. This communication is for information purposes only and should not be regarded as an offer to sell or as a solicitation of an offer to buy any financial product, an official confirmation of any transaction, or as an official statement of Lehman Brothers. Email transmission cannot be guaranteed to be secure or error-free. Therefore, we do not represent that this information is complete or accurate and it should not be relied upon as such. All information is subject to change without notice. 
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