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Re: Why RDF was a good choice

From: Carl Binding <cbd@zurich.ibm.com>
Date: Tue, 11 Jun 2002 08:51:11 +0200
To: "Sam Lerouge" <sam.lerouge@rug.ac.be>
Cc: www-mobile@w3.org, www-mobile-request@w3.org
Message-ID: <OF13DFFF7D.E36D7A53-ONC1256BD5.0024E1A6@LocalDomain>


Sam,
thanks for the answer; I see the point you're making and agree with the
fact that XSD does not offer this deducing capabilities. Mind you however
I'm not entirely convinced that
a) applications will really be able to make use of sophisticated deduction
and b) if such sophisticated deduction will ever be needed to describe,
after all, a limited set of
parameters for portable devices.

We see apps being driven through profiles and bearing in mind that UAProf
defines roughly 50 properties with - on the average - 3 possible values we
get 3^50 combinations. how shall
any application make sensible usage of this vast parameter space? Imagine a
JSP or Java Servlet based web application, which - in the end - produces
some markup. will application developers be able
to design good applications making usage of overly sophisticated and
fine-grain profile information?

XML Schema would, to some extent, probably support extensions through the
definition of new data types, but yes, this may not be as flexible as RDF
appears to be.

Eventually we'll face the issue of simplicity and useability vs academic
beauty.
Regards,
Carl



|---------+--------------------------->
|         |           "Sam Lerouge"   |
|         |           <sam.lerouge@rug|
|         |           .ac.be>         |
|         |           Sent by:        |
|         |           www-mobile-reque|
|         |           st@w3.org       |
|         |                           |
|         |                           |
|         |           10-06-02 16:42  |
|         |           Please respond  |
|         |           to "Sam Lerouge"|
|         |                           |
|---------+--------------------------->
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  |        To:      <www-mobile@w3.org>                                                                                                          |
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  |        Subject: Re: Why RDF was a good choice                                                                                                |
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Hello Carl,

The RDF model in itself perhaps does not provide any semantics advantages
compared to XML Schema, as far as I know (I am not an RDF expert). The
advantages come when you start using RDF Schema. Or better, when different
vocabularies are used, that refer to other vocabularies. These
"inter-vocabulary relationships" are not known in XML Schema, I believe.
The
previous version of the RDF Schema specification (see
http://www.w3.org/TR/2000/CR-rdf-schema-20000327/) gives some basic hints
on
how one could use this.
I think RDF is all about machine-readability, rather than
human-readability.
The interesting part of RDF is that a software agent that has a basic
knowledge on some constructs (e.g. the CC/PP model and core vocabulary) can
learn to use other vocabularies when you feed him a new RDF Schema that
refers to the vocabularies he already knows.
One strong point of RDF Schema is the ability to express of relationships
between different vocabularies. I am thinking of a useful application: when
a content provider knows that
a) "requested_file --mime-type--> image/jpeg", and
b) "user_agent --accepts--> [text/html, text/plain, image/jpeg,
image/gif]",
then he should be able to deduce the client will be able to process the
data. In order to do so, he must know the relationship between the
"mime-type" property, that belongs to a multimedia metadata vocabulary, and
the "accepts" property, that belongs to some CC/PP vocabulary. Using RDF
Schema (or one of the related technologies, such as DAML+OIL) to express
both vocabularies, and their relationships, would enable the content
provider to learn new vocabularies and their use.

Secondly, when I am thinking about "correct use" (I'd better say "proper
use") of RDF, I am thinking of using RDF Schemas to define vocabularies,
and
making use of the rdf:type property in RDF models. I think I wasn't very
clear about that in my previous mail.

Hope this wasn't too much information in one time.

Sam Lerouge
Received on Tuesday, 11 June 2002 02:52:25 GMT

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