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Re: Mistaken identity?

From: Dan Brickley <danbri@w3.org>
Date: Tue, 22 Jun 2004 07:38:12 -0400
To: Danny Ayers <danny666@virgilio.it>
Cc: www-rdf-interest@w3.org, distobj@acm.org, ken@bitsko.slc.ut.us, Norman.Walsh@Sun.COM
Message-ID: <20040622113812.GB4821@homer.w3.org>

* Danny Ayers <danny666@virgilio.it> [2004-06-22 13:20+0200]
> 
> I'm seeking a little clarification of the nature of identity on the web, 
> several related issues involved. In short, here are three little puzzles:
> 
> 1. Can a resource have multiple different representations of the same type?

Yes. eg. http://www.w3.org/Provider/Style/URI has at least English and
Spanish flavours, negotiable via HTTP.

> 2. If two resources have different sets of representations, can they 
> ever be considered the same?

If by 'same' you mean numerically identical, one-and-the-same, then no.
Everything true of the one, in that case, ought to be true of the other.

> 3. How can I ever assert:
> 
> <http://mydomain.org/a> owl:sameAs <http://yourdomain.org/a> .
> 
> when I can't ever be sure that you aren't going to change 
> http://yourdomain.org/a ?

owl:sameAs means identity in the strong sense above. I generally avoid
it in circumstances where change is reasonably likely. Note also that 
changes over time and other such real world nuisances (also provenance,
differences of perspective) aren't really visible to simple-minded 
systems like RDF and OWL. RDF/OWL software systems, on the other hand,
may well have coping mechanisms, APIs etc to help with life in the real
world.

This seems unfortunate until you realise how long it would've taken to 
standardise something that sophisticated...

Dan
Received on Tuesday, 22 June 2004 07:38:32 GMT

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