W3C home > Mailing lists > Public > public-data-shapes-wg@w3.org > May 2016

Re: Simplification of scopes section (see also ISSUE-148)

From: Karen Coyle <kcoyle@kcoyle.net>
Date: Sun, 15 May 2016 10:58:51 -0700
To: "public-data-shapes-wg@w3.org" <public-data-shapes-wg@w3.org>
Message-ID: <5738B8DB.6000103@kcoyle.net>
Can someone show how the shape below would be handled in ShEx? Thanks, kc

On 5/15/16 10:37 AM, Peter F. Patel-Schneider wrote:
> SHACL has allowed embedded shapes from the beginning.  Initially it allowed
> the embedding to be recursive, but this is currently not allowed.  One
> construct that allows recursive shapes is sh:valueShape.  See
> http://w3c.github.io/data-shapes/shacl/#constraints-shape for constructs that
> allow for embedded shapes, and
> http://w3c.github.io/data-shapes/shacl/#ValueShapeConstraintComponent for
> details on sh:valueShape.
>
> It is possible to have something like SHACL that does not do embedding at all.
>   SPIN works this way, I think.  Filters can also be used to get some of the
> effects of embedding, but I don't think that they are as expressive as embedding.
>
> However, there is a difference between filters and embedding in the validation
> results that would be returned.  Note that the validation results for ex:s1
> below are for a person who has a dependent without a SSN, not for the
> dependent.  A non-embedding filter solution would produce validation results
> for the dependent itself.
>
> peter
>
>
>
> On 05/15/2016 07:42 AM, Karen Coyle wrote:
>>
>>
>> On 5/14/16 1:08 PM, Peter F. Patel-Schneider wrote:
>>> One problem with having all shapes initiate validation is that embedded shapes
>>> would as well.
>>>
>>> So in
>>>
>>> ex:s1 rdf:type sh:Shape ;
>>>     sh:scopeClass ex:Person ;
>>>     sh:property [ sh:predicate ex:dependent ;
>>>                   sh:valueShape [ a sh:Shape ;
>>>                                   sh:property [ sh:predicate ex:SSN ;
>>>                                                 sh:minCount 1 ] ] ] .
>>>
>>> the scope of the embedded shape would be all nodes in the data graph,
>>> resulting in validation reports for any node that does not have a value for
>>> ex:SSN.
>>
>> I thought that filter shapes would be used if further refinement of the scope
>> is needed. This appears to be using a shape for that purpose (and I don't
>> recall this being mentioned before). Even with a defined scope it isn't clear
>> to me what the scope in the embedded shape would act on as its initial input,
>> since the spec says that a shapes graph is compared to a data graph, but the
>> result of scoping \= a new data graph. ? Anyway, is embedding shapes allowed?
>> If so, what are the rules for how that is implemented?
>>
>> kc
>>
>>>
>>> If all shapes are to have scopes then there are ways around this problem.  One
>>> would be that shapes are not embedded in other shapes.  Instead there would be
>>> a new kind of SHACL thing that is used when the current effect of embedding
>>> shapes in shapes is desired.
>>>
>>> peter
>>>
>>>
>

-- 
Karen Coyle
kcoyle@kcoyle.net http://kcoyle.net
m: 1-510-435-8234
skype: kcoylenet/+1-510-984-3600
Received on Sunday, 15 May 2016 17:59:16 UTC

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