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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@lehman.com]
Sent: Tue 9/10/2002 10:37 AM
To: Dare Obasanjo; Henry S. Thompson; Jeff Lowery
Cc: paul@prescod.net; Xml-Dev (E-mail)
Subject: RE: [xml-dev] 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@microsoft.com]
Sent: Tuesday, September 10, 2002 1:20 PM
To: Henry S. Thompson; Jeff Lowery
Cc: paul@prescod.net; Xml-Dev (E-mail)
Subject: RE: [xml-dev] 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@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
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@cogsci.ed.ac.uk
URL: http://www.ltg.ed.ac.uk/~ht/
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