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Re: recursive shapes in SHACL

From: Peter F. Patel-Schneider <pfpschneider@gmail.com>
Date: Wed, 25 Mar 2015 07:44:10 -0700
Message-ID: <5512C9BA.9030904@gmail.com>
To: Richard Cyganiak <richard@cyganiak.de>
CC: "public-data-shapes-wg@w3.org" <public-data-shapes-wg@w3.org>
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I'm not in favour of this kind of solution.

It splits the language in two.  It will be hard to describe.  It will
diminish interoperability.

peter

On 03/25/2015 07:34 AM, Richard Cyganiak wrote:
> 
>> On 24 Mar 2015, at 15:35, Peter F. Patel-Schneider
>> <pfpschneider@gmail.com> wrote:
>> 
>> I believe that the current design of SHACL 
>> (https://w3c.github.io/data-shapes/shacl/) will make recursive shapes
>> very problematic.
>> 
>> Both variations in 
>> http://w3c.github.io/data-shapes/shacl/#sparql-AbstractValueShapePropertyCo
nst
>>
>> 
raint
>> do not work correctly. (Consider how the designs would work on the
>> SHACL versions of the examples in 
>> https://lists.w3.org/Archives/Public/public-data-shapes-wg/2015Mar/0377.htm
l.)
>>
>>
>> 
Does anyone have a proposal on how to handle recursive shapes that does not
>> give rise to difficulties?
> 
> One possible design would be to have two language features,
> sh:valueShapeValidated and sh:valueShapeInformative.
> 
> sh:valueShapeValidated gives rise to a violation if the value doesn’t
> satisfy the specified shape. This is like the current sh:valueShape. But
> shape definitions with cycles of this features are illegal.
> 
> sh:valueShapeInformative allows cycles, but an implementation is not
> required to check it. In other words, an implementation may use any means
> of its own choice to determine whether it considers the value to be
> satisfying or not. One option is to do nothing, and accept any value.
> Another option is to do something clever with recursion. Another option
> is to inspect the URI given as the value. Another option is to check if
> the value has an rdf:type that has the required shape associated.
> 
> Best, Richard
> 
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Received on Wednesday, 25 March 2015 14:44:40 UTC

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