Object-oriented serialization (Was Re: Some questions)

David Megginson david at megginson.com
Thu Dec 2 11:44:29 GMT 1999

Matthew Gertner <matthew at praxis.cz> writes:

> I honestly feel that XML provides all the tools to do what RDF is trying
> to do, without an additional syntactic layer. What is missing from the
> picture is a mechanism for modelling object structures according to
> object-oriented principles, and this is why an OO schema language is
> necessary. 

If you have a function loadXML(), you get a DOM tree or a bunch of SAX
events or something similar; if you have a function loadRDF(), you get
a collection of objects with attributes and relationships.  In either
case, a schema can tell you things like "element type/class B is a
kind of element type/class A", but that's secondary information; the
primary information is "element X is an object of class Y with
identifier Z, while element A represents a relationship between this
object and object C".

If you're interested in a collection of objects in the first place,
why should you have to see or know about XML elements and attributes
at all?  Or to put it a different way, why should people constantly
have to redo the work of extracting objects from XML, when they're all
trying to do the same thing?

I think that reasonable people can argue that RDF is not the best
solution to the problem of object exchange in XML, but I am somewhat
surprised to hear people deny that the problem even exists: there is
an enormous demand for exchanging objects in XML (businesses exchange
a lot of structured data), and it's hard work to have to figure out
over and over how to construct objects from a SAX stream or a DOM tree
especially when programmers with XML knowledge are scarce and

I have no doubt that we need an abstract object layer on top of XML.
Right now, RDF is the best solution currently available (XMI also has
its advocates), but I'm ready to listen about anything better.

All the best,


David Megginson                 david at megginson.com

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