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From: Richard Cyganiak <richard@cyganiak.de>
Date: Wed, 4 Mar 2015 15:38:00 +0000
Cc: "public-data-shapes-wg@w3.org" <public-data-shapes-wg@w3.org>
Message-Id: <226A4F65-D556-471E-ABE0-C209EE7FE3D9@cyganiak.de>
To: "Peter F. Patel-Schneider" <pfpschneider@gmail.com>
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Subject: =?utf-8?Q?Re:_“SHACL_Minus_SPARQL”?

> On 4 Mar 2015, at 15:21, Peter F. Patel-Schneider <pfpschneider@gmail.com> wrote:
> Yes, I mean closed shapes, i.e., all triples in a graph (or around a node)
> have to be somehow consumed by the shape.
> I don't think that your idea of constructing the matched triples will work
> in the presence of disjunction, at least without considerable code embedded
> into the SPARQL engine.

You are probably right. I may investigate further if it is established that someone can’t live without this feature.


> peter
> On 03/04/2015 06:37 AM, Richard Cyganiak wrote:
>>> On 3 Mar 2015, at 21:49, Peter F. Patel-Schneider
>>> <pfpschneider@gmail.com> wrote:
>>> I would like to see the core of a proposal for something that would
>>> support "SHACL minus SPARQL" as well as the core of a proposal for
>>> "SHACL plus SPARQL".
>>> I think that I could fairly easily put together a proposal for most of
>>> the former, but I am puzzled as to how to handle recursion and closure,
>>> so I would like to see how a proponent of this approach would handle
>>> recursion or closure.
>> By closure, do you mean “closed shapes” as described here? 
>> https://www.w3.org/2014/data-shapes/wiki/Requirements#Expressivity:_Closed_Shapes
>> I’m not sure that this can be easily supported.
>> One way to do it might be to attach a second bit of SPARQL to each “macro
>> definition”/“shape node”. That bit of SPARQL would CONSTRUCT the triples
>> that are considered to be “covered” by a successful “macro”/“shape”
>> evaluation. A SHACL processor would collect all those triples, and if any
>> triples in the input RDF graph under consideration are not among those
>> “covered”, then the closedness constraint is violated.
>> Personally I’m not fully convinced that this requirement is a good idea
>> and necessary for SHACL 1.0, and there are many cases where I don’t know
>> what the desired behaviour would be. I’d be quite comfortable with
>> postponing this to a future version of SHACL.
>> My thoughts on recursion are too muddled to be of much help.
>> Best, Richard
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Received on Wednesday, 4 March 2015 15:38:26 UTC

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