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Re: Cambridge Communique

From: Pierre-Antoine CHAMPIN <champin@cpe.fr>
Date: Fri, 12 Nov 1999 11:20:02 +0000
Message-ID: <382BF7E2.357384E0@cpe.fr>
To: www-rdf-interest@w3.org
Here is my faith about the fight XML-schema vs. RDF-schema :)

First of all, I don't think they should merge,
and I don't think there is such an ambiguity
between using one or the other...
Even if you can do about the same thing with both,
they are not designed for the same purpose :

1) XML DTDs and XML-schema allow to specify LANGUAGES.
Those languages allow us to write documents,
from a love letter to a database serialization.

2.a) RDF is an instance of XML
Yes, RDF is a plain instance of XML.
The fact that there is no DTD nor XML-schema is not a problem,
since we could write RDF with 2 tags <Description> and <Property>
and keep the same power of expression.

2.b) RDF allows to DESCRIBE RESOURCES
Since resources are typically web resources, that is, pieces of data,
RDF documents can be considered as META-DATA.

2.c) RDF documents are structured
They look more like a database than like a love letter.

3) RDF-schema allows to DEFINE resources useful for describing other ones.
That is, Classes and Properties.
And since RDF-schemas are expressed in RDF,
we can also describe those resources (with domain and range, for example).

So where is the problem ?
We express standard documents (that is, data) in XML, with XML schema,
and metadata with RDF and RDF-schema.
Where is the problem ?

The problem is in the definition of RESOURCE.
For RDF, virtually ANYTHING can be considered as a resource.
And since any document usually talks about SOMETHING,
well any document contains metadata!
Another point is that XML,
which was initially meant to be used for expressing any kind of document,
is now usually seen as a structured data language.

This might sound a bit caricatural,
but I think this is why so many people are confused about using XML or RDF.
I don't have any recipe for when using XML or RDF,
but I think the right questions are :

* how much structured will my document be ?
* what is it talking about, and do I have interest
  in considering it as resources ?

 Pierre-Antoine
Received on Friday, 12 November 1999 05:24:34 GMT

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