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Re: Comment on Entailment Regimes

From: Holger Knublauch <holger@topquadrant.com>
Date: Fri, 17 Feb 2017 14:19:21 +1000
To: public-rdf-shapes@w3.org
Message-ID: <0c409a41-2364-257c-1b00-dd8690ba1e69@topquadrant.com>
Hi Lars,

thank you for your comment.

Your description of the situation is correct. As you have suggested, I 
have moved the Appendix A into section 1.5, see

https://github.com/w3c/data-shapes/commit/a98a3e54d17f15418dde487198d0462af02c68b6

The reason why it ended up in an appendix in the first place was that we 
felt it neither belonged into SHACL Core nor SHACL-SPARQL. But it does 
indeed belong into both, and I agree that that flow has improved now. On 
this occasion I have also added the formal syntax rule for 
sh:entailment's node kind and have attempted to address the question 
about multiple values. The intent of the current prose is to indicate 
that all inferred triples must be present for all entailment regimes.

If you have further suggestions on this aspect, please suggest specific 
changes to the wording. If you have further comments on other topics 
(good or bad), please keep them coming.

Regards,
Holger


On 16/02/2017 19:25, Svensson, Lars wrote:
> Hello all,
>
> Looking at the current editor's draft [1] I have a question / comment on the use of entailment in SHACL processing.
>
> §1.5 [2] states normatively that "SHACL uses the RDF and RDFS vocabularies, but full RDFS inferencing is not required" and then goes on _non-normatively_ to talk about the property sh:entailment and how SHACL processors may support RDFS entailment (or any other kind of entailment).
>
> When I first read this, I felt confused since the normative part says that RDFS inferencing is not required but that SHACL processors MAY support it, leaving me wondering if that meant that different processors might come to different results depending on whether they support inferencing or not. The answer came further down in Appendix A [3] where it is stated that "if an entailment regime is provided in the shapes graph which is not supported by the SHACL processor, the validation MUST produce a failure" which is clear enough.
>
> I would find it easier for the reader, though, if you would remove Appendix A and move its contents to §1.5 so that you have all the information about entailment in one place. Further, there seems to be no formal definition of sh:entailment in the document. The property is only mentioned in the non-normative part of §1.5 and in Appendix A (which I don't know if it's normative or not: Are appendices normative?). I guess that it is (theoretically) possible to ask the SHACL processor to use more than one entailment regime (e. g. RDFS [4] and D-entailment [5]) but that the support of that is implementation-specific. It would help, though, if there were a (non-normative) note about that in the spec, too.
>
> [1] https://w3c.github.io/data-shapes/shacl/
> [2] https://w3c.github.io/data-shapes/shacl/#shacl-rdfs
> [3] https://w3c.github.io/data-shapes/shacl/#entailment
> [4] https://www.w3.org/TR/sparql11-entailment/#RDFSEntRegime
> [5] https://www.w3.org/TR/sparql11-entailment/#DEntRegime
>
> Thanks,
>
> Lars
>
> *** Lesen. Hören. Wissen. Deutsche Nationalbibliothek ***
Received on Friday, 17 February 2017 04:19:59 UTC

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