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Re: Why is RDF such a tough sell?

From: James Tauber <jtauber@jtauber.com>
Date: Tue, 25 Jun 2002 02:18:21 +0800
Message-ID: <004201c21bab$871b0e10$8520f0d4@HARRY>
To: <MDaconta@aol.com>, <www-rdf-interest@w3.org>

> So, although this issue has many angles, I'd like to begin with
> this question, "Are RDF and Schema competitors?"

XML schema languages are principally about constraining the surface syntax
of a class of XML documents.

RDF is principally about expressing the properties of and relationships
between objects (and an RDF *schema* about constraining those properties and
relationships).

Consider

    <Person>
        <Name>James</Name>
    </Person>

The XML view of this is "element of name 'Person' with child element of name
'Name' with character data 'James'". An XML schema can say things like "a
'Person' element can contain a 'Name' element".

The RDF view of this is "there is a class of objects designated 'Person' and
this particular person has a 'Name' of 'James'." An RDF schema can say
things like "objects of the type 'Person' can have 'Name's".

So RDF is considerably more perspicuous in modelling data. 'Name' is a valid
property of a 'Person' is generally more insightful than 'Name' is a valid
sub-element of 'Person'. In a sense RDF is more fundamental than XML as it
about the nature of the data, not just some particular serialization of it.
Of course, any collection of objects and their relationships can be
expressed in XML but you have to then decide how the relationships and
properties are going to map to elements and attributes (and vice versa on
the other end).

Put another way, RDF is about the fact that 'A' is the letter 'A' whereas
XML is about with the fact that in ASCII 'A' is the octet '01000001'. You
need something like the latter to move the things about, but the former is
what you ultimately care about.

James
Received on Monday, 24 June 2002 14:18:57 GMT

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