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Skolemization Proposal in RDF 1.1 working draft

From: Alan Ruttenberg <alanruttenberg@gmail.com>
Date: Sat, 14 Jul 2012 17:45:57 -0400
Message-ID: <CAFKQJ8mR9j1BjQ46RGfi8tSZbsW7bu2SG1o-NGLpBX61zNbdfg@mail.gmail.com>
To: Michael Schneider <schneid@fzi.de>
Cc: Pat Hayes <phayes@ihmc.us>, David Booth <david@dbooth.org>, "semantic-web@w3.org" <semantic-web@w3.org>, OWL Working Group <public-owl-wg@w3.org>
On Saturday, July 14, 2012, Michael Schneider wrote:

> Hi Alan!
>
> Am 14.07.2012 19:15, schrieb Alan Ruttenberg:
>
>  "Blank nodes do not have identifiers in the RDF abstract syntax. The
>> blank node identifiers introduced by some concrete syntaxes have only
>> local scope and are purely an artifact of the serialization."
>>
>> It is incorrect that blank notes are purely an artifact of
>> serialization. In *any*  serialization that I am aware of. Please
>> correct me if I am wrong.
>>
>
> The text you cite talks about blank node *identifiers*, the often
> crazy-looking strings that are created by Jena or the OWL API to represent
>  blank nodes, and which often happen to be different after an RDF graph is
> parsed from a file and then written back to another file.


All right, then I consider that poor expression. These aren't in a syntax
that has identifiers with local scope. There at indeed tools that generate
those things.  My experience is they are interal to implementations  If I
see them in a serialization I consider it a bug.

In any case, those internal things don't seem to be what is proposed here.
Rather it appears that this gives sanction to *rewriting* graphs to be
different graphs (spec saya "tranformed") and my concern is that this
rewriting process will destroy OWL serializations.

As I tried to suggest in my previous note, people can choose to mangle
their triples however they want. But the RDF spec shouldn't sanction a
change that amount to a backwards incompatible change to the behavior of
systems that other specifications depend on. The suggestion that this be
implemented in Sparql was an attempt to make is so that users would only
see this sort of thing if they requested it.

There are other ways something similar could be accomplished , for example
the syntaxes could provide mechanisms for annotating blank nodes with
identifiers without disturbing existing expectations. E.g. This could be a
specification of how the value of the nodeid attribute in rdfxml can
behave.

-Alan



> The text does not talk about the blank nodes themselves, which are part of
> the abstract model of RDF.
>
> Cheers,
> Michael
>
> PS: The next one to send a reply might consider changing the subject. :-)
>
> --
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Received on Saturday, 14 July 2012 21:46:26 GMT

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