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Re: [RDF-CONCEPTS] Skolemization

From: David Booth <david@dbooth.org>
Date: Sun, 16 Jun 2013 19:51:35 -0400
Message-ID: <51BE4F87.1010504@dbooth.org>
To: Ivan Herman <ivan@w3.org>
CC: Niklas Lindström <lindstream@gmail.com>, Pat Hayes <phayes@ihmc.us>, public-rdf-comments <public-rdf-comments@w3.org>
On 06/16/2013 06:22 AM, Ivan Herman wrote:
> I have not looked at the text right now (I am on a mobile), and that may be good
> at this moment, because it shows what I remember the intention was...
> I guess the question of David could/should be boiled down to: is the
> Skolemization part normative or not? I think we never meant that to be normative
> in the group; if it says so in the document, that is a mistake (Pat already
> alluded to that). If it is non normative, then the usage of an RFC MUST would
> become fairly meaningless... Is there any reason we would make it normative?
> This request never came up in the group before; the whole skolemization was
> presented as a good practice to follow if one wants to get rid of bnodes when
> exchanging graphs.
> (Systems may skolemize for any other reason, eg, for internal purposes or
> exchanging data with other instantiation of the same software only, and they may
> decide to use some sort of a UUID based URI which would be just as fine. If we
> set a 'must' for the genid way, then a UUID based skolemization might be
> considered as illegal:-(

aha!  I think I see where the confusion lies, and I apologize for not 
noticing this sooner.  :(

I believe we are talking about two different kinds of skolemization. 
the first is what I will call *unconstrained* skolemization, and this is 
the process of properly substituting arbitrary new IRIs for bnodes.  for 
this, any kind of IRI  will do.  the second I will call 
*round-trippable* skolemization, and this *requires* that the IRIs be 
minted using the "genid" well-known suffix, so that they can be 
Predictably recognized by other parties.

the definition of *unconstrained* skolemization does not need to be 
normative, because other parties will not be depending on recognizing 
its result.  but the definition of *round-trippable* skolemization 
*does* need to be normative, so that other parties acting independently 
can Predictably recognize the *round-trippable* skolem IRIs and turn 
them back into bnodes if desired.

does that make more sense now?

Received on Sunday, 16 June 2013 23:52:04 UTC

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