[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message]

Re: Inheritance in XML


mohammad ghazal
I just recalled a July 2003 thread on the Federal CIO Council XML Web
Services Working Group listserv in which a writing by Norm Walsh on this
very topic was referenced[1]. Subject: "XML is Not Object Oriented". I
provided a somewhat lengthy contribution[2].

Kind Regards,
Joe Chiusano
Booz | Allen | Hamilton
Strategy and Technology Consultants to the World

[1]
http://listserv.gsa.gov/cgi-bin/wa?A2=ind0307&L=cioc-web-services&F=&S=&P=1267
[2]
http://listserv.gsa.gov/cgi-bin/wa?A2=ind0307&L=cioc-web-services&F=&S=&P=2510
Burak Emir wrote:
> 
> Chiusano Joseph wrote:
> 
> >Elliotte Rusty Harold wrote:
> >
> >
> >>At 12:14 AM +0200 6/18/04, Mohammad Ghazal wrote:
> >>
> >>
> >>>Dear Sir,
> >>>      I would like to know the relation between XML and the
> >>>Inheritance/Subtype concepts, I have read from several books and I
> >>>
> >>>
> >>>
> >>It's roughly the same as the relationship between a grapefruit and a
> >>bicycle. That is, there isn't one. :-)
> >>
> ...
> 
> >I would add that W3C Schema has some features that one can say involve
> >inheritance, such as derivation by extension. But the bottom line is
> >that it's all about how one chooses to use XML.
> >
> >
> 
> There was a quite controversial panel at ECOOP 2004 which talked about
> XML and objects. http://www.ifi.uio.no/ecoop2004/
> 
> For Eric Meijer, XML was just a way to serialize (XEN or C-omega)
> objects - hence, I guess, you could say there is a relation, because
> objects have subtyping and inheritance, so you can somewhere use XML to
> model it.
> 
> My take was this: With XML you can, among other things, represent data,
> such as the *state* of an object.
> 
> The derivation by extension then comes close to inheritance, because
> your derived type has all the data of the type you derived it from.
> 
> A derived type is a bit like a subtype - you can, in principle, use it
> everywhere where the original type (like the supertype) is expected.
> However, you have to annotate the enclosing element using the xsi:type
> attribute.
> 
> BUT this is all very far away from the kind of inheritance and subtyping
> in OOP because inheriting the behaviour of objects (the methods)
> interacts with other things like overloading, overriding, refining.
> 
> For instance, some languages (not Java) would allow you to have classes
> class Author;
> class BookAuthor extends Author;
> class Publication { val author:Author }
> class Book{ override val author: BookAuthor } extends Publication
> 
> I do not think specialising the type of author (say, the first element
> in XML element content) can be done with XML Schema
> derivation-by-restriction, because restriction (and in general all
> schema types) speak about structure (restriction means regular language
> inclusion, it is not covariant, if you will).
> 
> So in essence, you seem to get a form of inheritance for *state* with
> derivation-by-extension. To do subtyping etc. you do need much more than
> that, e.g. build a data binding framework that makes your classes
> correspond to W3C XML Schema derived types + something more.
> 
> hope this helps. cheers,
> Burak

-- 
Kind Regards,
Joseph Chiusano
Associate
Booz | Allen | Hamilton

PURCHASE STYLUS STUDIO ONLINE TODAY!

Purchasing Stylus Studio from our online shop is Easy, Secure and Value Priced!

Buy Stylus Studio Now

Download The World's Best XML IDE!

Accelerate XML development with our award-winning XML IDE - Download a free trial today!

Don't miss another message! Subscribe to this list today.
Email
First Name
Last Name
Company
Subscribe in XML format
RSS 2.0
Atom 0.3
 

Stylus Studio has published XML-DEV in RSS and ATOM formats, enabling users to easily subcribe to the list from their preferred news reader application.


Stylus Studio Sponsored Links are added links designed to provide related and additional information to the visitors of this website. they were not included by the author in the initial post. To view the content without the Sponsor Links please click here.

Site Map | Privacy Policy | Terms of Use | Trademarks
Free Stylus Studio XML Training:
W3C Member
Stylus Studio® and DataDirect XQuery ™are products from DataDirect Technologies, is a registered trademark of Progress Software Corporation, in the U.S. and other countries. © 2004-2013 All Rights Reserved.