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Re: [RDF-CONCEPTS] Skolemization

From: Andy Seaborne <andy@apache.org>
Date: Mon, 17 Jun 2013 12:14:05 +0100
Message-ID: <51BEEF7D.3030805@apache.org>
To: public-rdf-comments@w3.org
On 17/06/13 10:52, Markus Lanthaler wrote:
> On Monday, June 17, 2013 11:37 AM, Andy Seaborne wrote:
>>>> 3/ globalization (giving a recognizable identify to the bnode outside
>>>> it's original context/data; the bnode is now transferrable to other
>>>> systems; other systems can reverse the process)
>   >
>>> Wouldn't that mean that a Skolem IRI === bNode and thus be at odds
>>> with the definition of bnodes: "The blank nodes in an RDF graph are
>>> drawn from an infinite set. This set is disjoint from the set of all
>>> IRIs and the set of all literals".
>> It's giving a name so it's not identity.  It's not happening at the
>> level of semantics or the proper data model. You can think of it as a It
>> is extending 2 to create a tunnel for blank nodes within the RDF 1.1
>> syntax.  The fact that the rules for skolemization are now published (in
>> 2, they are not) makes it different.
> I'm not sure I understand the distinction. To me it looks like a hack to
> serialize a blank node using a IRI even though "everyone" knows that it is a
> blank node. In case someone doesn't know (because it blindly treats IRIs as
> IRIs) and uses that that skolem IRI in his own data (e.g. by referencing
> it), the system would break down. IRIs are global identifiers, blank nodes
> are local identifiers. I can't see how you can have both at the same time.

I'm not proposing an approach - I just outlined some different usages 
that seem, to me, to be behind the discussion.

You picked === (identity equality, not equivalence) which I understood 
to be that a claim that the IRI is identical to the bNode.  IRIs do not 
work like bNodes - we're agreed on that - that's at the model theory 
level.  Skolemization looses something, we need to make sure it isn't a 
harmful loss.


> --
> Markus Lanthaler
> @markuslanthaler
Received on Monday, 17 June 2013 11:14:39 UTC

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