XML [~serialization] and Objects

Dan Brickley Daniel.Brickley at bristol.ac.uk
Tue Sep 29 21:01:57 BST 1998

On Tue, 29 Sep 1998, David Brownell wrote:
> >  one
> > wants to be able to use an XML element to represent some sort
> > of 'thing' (avoiding the word object), and it should be possible
> > for multiple applications to use this XML document, each one
> > possibly wishing to instantiate the 'thing' using a different class.
> In the general case I'd go so far as to say that _some_ elements
> represent a "thing", and many don't.  Existing DTDs aren't all done
> with a particular object modeling paradigm, and so on.  One can't
> deduce which elements represent objects, which represent properties,
> which represent actions, and so forth without a data model in hand.

Quite. There's yet another variant on the XML/OO serialisation idea
at:  "Java Serialization Using RDF with Schemas"
http://wave.eecs.wsu.edu/CKRMI/JSRDF.html  (appears to require Java1.1
browser though), which gets around this by using RDF/XML, since RDF
introduces conventions that do let you deduce, for previously
unencountered vocabularies, which constructs refer to properties,
classes and so on.

BTW there's a slight mismatch between RDF's notion of a "class" and Java's;
RDF allowers more free-flowing annotation, so you can attach properties 
(eg. price, color) to resources that belong to a class whose original
definition didn't anticipate such annotations. Properties are defined in
terms of the class they're applied to and the type of value they have; I
believe the post below refers to an earlier version of RDF Schemas where
each class had associated "allowedPropertyTypes". In practice this was
essentially the same mechanism as the domain/range mechanism now on
offer <http://www.w3.org/TR/WD-rdf-schema/>, although
allowedPropertyType had a more OOish feel.


Original RDF-DEV post follows:

> To further understand RDF with Schemas, people (especially
> Java developers) might want to take a look at our pages on
> "Java Serialization Using RDF with Schemas" at the address
> http://wave.eecs.wsu.edu/CKRMI/JSRDF.html.

> Here we automatically translate all packages and classes
> in the Java API into RDF/Schemas, we give some source code,
> and we also translate an example of Bill LaForge's which
> demonstrates Java Serialization using RDF/Schemas of some
> simple Java classes and instances that have inheritance, arrays,
> and reference loops.

> Robert
> _________________________________________________

> Robert E. Kent email: rekent at eecs.wsu.edu

Daniel.Brickley at bristol.ac.uk                           
Institute for Learning and Research Technology   http://www.ilrt.bris.ac.uk/
University of Bristol,  Bristol BS8 1TN, UK.     tel: +44(0)117 9288478

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