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Re: Guide Comments: Suggested response w/ question

From: Jeremy Carroll <jjc@hpl.hp.com>
Date: Fri, 2 May 2003 22:02:44 +0300
To: www-webont-wg@w3.org
Message-Id: <200305022202.44571.jjc@hpl.hp.com>


sorry, forgot, S&AS does not conflict ...

the sentence quoted was concerning the abstract syntax, which is well removed 
from surface representation issues such as XML Base. 

The usage of xml:base that already happens, for example with our owl:imports 
test cases, is that the xml:base and rdf:about idiom specifies a logical 
location, and the document might actually have been retrieved from somewhere 
else, such as in a zip file, or a local cache.

The S&AS sentence does suggest that it would be a mistake to use a URL for an 
ontology that was different from the one that can be retrieved from that URL; 
and would discourage the use of a non-retrievable URI with some private 
mechanism to relate URIs with ontologies. (The Web get action is the ontology 
retrieval action). The quotes from Guide do not contradict this.

A further reason why the xml:base mechanism is good is that many different 
URLs retrieve the same physical bits. By including an xml:base within the 
bit-stream then one of those equivalent URLs is given as preferenced, by the 
document author. This minimizes the need for the receiver to make good.

e.g.

http://www.w3.org/2002/07/owl

can be retrieved with:

http://www.w3.org/2002/07/owl.rdf
HTTP://www.w3.org/2002/07/owl
http://www.w3.org:80/2002/07/owl
HTTP://18.7.14.127/2002/07/owl.rdf

However, because of the xml:base in it, all of these correspond to identical 
RDF graphs.

See
http://www.w3.org/RDF/Validator/ARPServlet?PARSE=Parse%20URI:%20&URI=HTTP://18.7.14.127/2002/07/owl.rdf

Jeremy
Received on Friday, 2 May 2003 16:02:35 GMT

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