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Re: Usage of xml:base in OWL--different from DAML?

From: Jeremy Carroll <jjc@hpl.hp.com>
Date: Fri, 16 May 2003 18:49:19 +0300
To: www-rdf-logic@w3.org
Message-Id: <200305161849.19182.jjc@hpl.hp.com>

> I read some of the differences between DAML+OIL and OWL[1] and nothing
> about character strings, or values of xml:base was mentioned.

xml:base was added to RDF/XML relatively recently, I guess about a year ago.
Formally it still is not added in that the current recommendation is RDF Model 
and Syntax which does not include support. It is included in the RDF Syntax 
working draft.

If your DAML tool uses an older RDF parser then you will get an error with 
DAML+OWL or OWL that uses RDF/XML idioms that are only in the newer drafts.

I notice you took your example from OWL Test Cases - these examples are all 
validated against the RDF Working Drafts, rather than the older Model and 
Syntax recommendation.

Moreover, all the OWL Test cases use xml:base see:

http://lists.w3.org/Archives/Public/www-webont-wg/2003May/0021.html

[[
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, 16 May 2003 12:49:10 GMT

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