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Re: Choreography and the Semantic Web

From: Mark Baker <distobj@acm.org>
Date: Tue, 13 Aug 2002 09:37:09 -0400
To: Christopher B Ferris <chrisfer@us.ibm.com>
Cc: www-ws-arch@w3.org
Message-ID: <20020813093709.A20563@www.markbaker.ca>

On Mon, Aug 12, 2002 at 10:40:58AM -0400, Christopher B Ferris wrote:
> > SOAP and WSDL do very different things than RDF does.  SOAP and WSDL
> > can't be used to express the state of any resource; you can't use them
> > to say "the temperature is 33 degress celsius", for example.
> Nonsense! 

All WSDL can do is describe the *interface* to a service that can return
the temperature.  That is an entirely different thing than what RDF
does, which is to provide a model that allows data to assert that the
temperature is such-and-such a value.

WSDL is typically used (and principally supports) an early-binding mode
of operation, so the client knows it's dealing with a thermometer, and
therefore any data returned is known to be a temperature value.  REST,
by virtue of being late bound, wouldn't know what the string "33" meant
because the URI it invoked GET on is opaque to it, and it doesn't have
any other info to go on.  So the data returned has to describe the type
(and value, and relationships, etc...), which "33" doesn't.  This is
what RDF does, and why it (or something similar, right Frank 8-) is
critically required for machine processing on the Web.

As I said, it's no wonder Web services proponents don't generally see
the value in RDF, because so much information about what you're
interacting with is already known a priori.

Mark Baker, CTO, Idokorro Mobile (formerly Planetfred)
Ottawa, Ontario, CANADA.               distobj@acm.org
http://www.markbaker.ca        http://www.idokorro.com
Received on Tuesday, 13 August 2002 09:36:28 UTC

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