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Re: regrets & skolem predicates

From: Pat Hayes <phayes@ihmc.us>
Date: Wed, 20 Apr 2011 16:18:34 -0500
Cc: William Waites <ww@styx.org>, RDF-WG <public-rdf-wg@w3.org>
Message-Id: <6A9DB2F5-30B0-4A83-B648-D8AD5AFFB2FC@ihmc.us>
To: Alex Hall <alexhall@revelytix.com>

On Apr 20, 2011, at 9:33 AM, Alex Hall wrote:

> On Wed, Apr 20, 2011 at 10:20 AM, William Waites <ww@styx.org> wrote:
> Unfortunately I won't be able to make the call today due to a
> conflicting commitment.
> However, a thought just occurred to me - what happens when someone
> uses a skolem constant - now a URI - as a predicate?
> No problem with this, as far as I can see.  What's to say that the resource denoted by that blank node doesn't have a URI that could be used as a predicate if we knew it?
> If the system that created the skolem constant wants to translate that constant back into the original blank node when inserting in the graph, presumably it would have to disallow that.  But such systems already have checks in place, e.g. to discard statements with literal subjects resulting from an INSERT with a variable in the subject position.

BTW, I can't help pointing out that if we had the authority to allow literals in subject position, then we could invent a simple literal scheme for skolemization, along the lines "<text-of-bnode-id-label>"^^yourBaseUri:genid, giving all the benefits of the unique global URI system without the need to get involved with tiresome licencing issues. 

But this simple and elegant solution will have to be put onto the scrapheap of history, along with all the other elegant simplifications that would accrue from correcting this silly conceptual bug in RDF :-)


> -Alex
> Cheers,
> -w
> --
> William Waites                <mailto:ww@styx.org>
> http://river.styx.org/ww/        <sip:ww@styx.org>
> F4B3 39BF E775 CF42 0BAB  3DF0 BE40 A6DF B06F FD45

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Received on Wednesday, 20 April 2011 21:19:24 UTC

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