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Re: OWL/RDF Ref/Def and Namespace Reference?

From: Dan Brickley <danbri@danbri.org>
Date: Mon, 13 Jul 2009 13:47:58 +0200
Message-ID: <4A5B1EEE.4020100@danbri.org>
To: Brad Cox <bradjcox@gmail.com>
CC: public-owl-dev@w3.org
On 13/7/09 13:23, Brad Cox wrote:
> Thanks Bijan. That leaves just one puzzler. Why is it
> foaf:imaginaryFriend not foaf#imaginaryFriend,

Because 9 nears ago, I similarly dispaired on these same issues, flipped 
a coin, and decided that the FOAF ns URI would end in a slash: 
"http://xmlns.com/foaf/0.1/". In the RDF/XML syntax, foaf:foo 
concatenates imaginaryFriend onto that base.

> and which should I use
> for my own properties from my core: (core#?) namespace?

Lately, # is more popular. However you might think twice if your 
namespace contains a lot of stuff, eg. 1000s of terms.

> I've been doing it like this, confused by when to use core: vs core#
>
> <rdf:Description rdf:about="#SomeModelElement">
> <rdf:type
> rdf:resource="http://<host>/ontology/2009/07/core#SomeElementClass"/>
> <core:isElementOf rdf:resource="#SomeModel"/>
> <core:hasStakeholder rdf:resource="#SomeStakeholder"/>
> <rdfs:comment>Some Comment</rdfs:comment>
> </rdf:Description>
>
> Seems to work. But how to explain why to newcomers? I couldn't.

The XML namespace abbrevations only work between "<" and ">", elsewhere, 
full or relative URIs are needed.

> PS: One other. I thought rdf:ID="SomeName" was *THE* way to *define* a
> new item that you *know* doesn't exist and rdf:about="#SomeName" was
> *THE* way to reference or extend one that might not yet exist.

Yep, the original 1997-9 specs did suggest that. But the concept was 
somewhat confusing, and wasn't evident in the triples that come out of 
RDF parsing, so got downplayed somewhat in the 2004 revised RDF specs 
(http://www.w3.org/TR/2004/REC-rdf-syntax-grammar-20040210/#section-Syntax-ID-xml-base 
).

>  Why
> there's about= and resource=, I've never understood.

A misplaced attempt at natural-language readability, I think. In the 
first published draft of RDF/XML, it was "href" 
(http://web5.w3.org/TR/WD-rdf-syntax-971002/). The word "about" kinda 
makes sense when the element is the content-less wrapper "Description" 
rather than a class name, ie. it's a "description about" something.

cheers,

Dan
Received on Monday, 13 July 2009 11:48:40 GMT

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