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Re: namespace declarations and imports

From: Michael Hausenblas <michael.hausenblas@deri.org>
Date: Wed, 24 Jun 2009 09:40:42 +0100
To: James Prentice <prentice.j.a@gmail.com>
CC: Semantic Web community <semantic-web@w3.org>
Message-ID: <C667A51A.5E1B%michael.hausenblas@deri.org>


IMHO a pre-linked-data-area issue. See the recent discussion on
public-lod@w3.org mailing list [1], hence not sure if it makes sense to
rehash it here.


[1] http://lists.w3.org/Archives/Public/public-lod/2009Jun/0243.html

Dr. Michael Hausenblas
LiDRC - Linked Data Research Centre
DERI - Digital Enterprise Research Institute
NUIG - National University of Ireland, Galway
Ireland, Europe
Tel. +353 91 495730

> From: James Prentice <prentice.j.a@gmail.com>
> Date: Tue, 23 Jun 2009 16:18:06 -0700
> To: Semantic Web community <semantic-web@w3.org>
> Subject: namespace declarations and imports
> Resent-From: Semantic Web community <semantic-web@w3.org>
> Resent-Date: Wed, 24 Jun 2009 08:22:05 +0000
> I have a very newbie question I'm hoping someone can clarify. Say I'm
> creating an ontology and have several namespace declarations because I want
> to use some defined vocabularies, e.g. foaf:http://xmlns.com/foaf/0.1/ and
> owl:http://www.w3.org/2002/07/owl#. Maybe I want to use foaf:mbox and
> owl:sameAs. My question is, how are the foaf and owl definitions located?
> Since URIs are not always resolvable, or may be resolvable to something
> other than the ontology itself, I'm wondering how they are loaded when I do
> something like run the Pellet reasoner on my ontology in Protege. Does it
> look up the URI in some common repositories and try to load from there?
> On a related note, I was confused by this paragraph from
> http://www.w3.org/TR/owl-ref/#imports-def
> "Although owl:imports and namespace declarations may appear redundant, they
> actually serve different purposes. Namespace declarations simply set up a
> shorthand for referring to identifiers. They do not implicitly include the
> meaning of documents located at the URI. On the other hand, owl:imports does
> not provide any shorthand notation for referring to the identifiers from the
> imported document. Therefore, it is common to have a corresponding namespace
> declaration for any ontology that is imported."
> Namespace declarations don't *only* set up shorthand, do they? If I declare
> the foaf namespace and then refer to foaf definitions in my ontology, at
> some point the foaf ontology has to be loaded. I don't see a large
> difference between namespace declarations and imports.
> I'm very confused by this issue, so it's possible that my question doesn't
> even make sense. :-) Thanks for any clarification of this issue.
> Cheers,
> Jim
Received on Wednesday, 24 June 2009 08:41:35 UTC

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