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Re: A question on sh:xone and sh:targetObjectsOf

From: Holger Knublauch <holger@topquadrant.com>
Date: Sat, 8 Sep 2018 11:02:19 +1000
To: public-shacl@w3.org
Message-ID: <ffe9fbdf-7fb6-9d37-9cca-91b11593c3c7@topquadrant.com>
Hi Gary,

there is no sh:xor in SHACL, so we can remove that from the discussion. 
If you had results with this then sh:xor didn't have any effect to the 
validation.

Also you seem to want to use sh:targetXY statements as a validation 
condition. If I understand what you are trying to express as "not used 
as a value of schema:review" then

     sh:not [ sh:targetObjectsOf schema:review ] ;

needs to be rewritten using sh:max/minCount, maybe

     sh:property [
         sh:path [ sh:inversePath schema:review ] ;
         sh:maxCount 1;
     ] ;

The above would walk schema:review "backwards" starting at the focus 
node (instance of AggregateRating).

Maybe this informs your next steps?

Holger


On 8/09/2018 6:00 AM, Gary Murphy wrote:
> I have a novice question about setting alternatives in a NodeShape 
> using sh:xone, sh:xor and sh:or
>
> I need to evaluate a property of the targetClass such that, if the 
> node is targetObjectsOf a property in another node, then a particular 
> property should not be defined, but if not, then it is -- this pattern 
> occurs several times in schema.org <http://schema.org> validation rules.
>
> So for example, here was my naive attempt using sh:xone but also with 
> sh:xor and sh:or ...
>
>     hmshape:AggregateRatingShape
>         a sh:NodeShape ;
>     sh:targetClass schema:AggregateRating ;
>     sh:property [
>     sh:xone (
>      [
>        sh:not [ sh:targetObjectsOf schema:review ] ;
>        sh:path schema:itemReviewed ;
>        sh:minCount 1 ;
>        sh:severity sh:Error ;
>      ]
>      [
>        sh:targetObjectsOf schema:review ;
>        sh:path schema:itemReviewed ;
>        sh:maxCount 0 ;
>        sh:severity sh:Warning ;
>      ]
>      ) ;
>      ] ;
>         .
>
>
> and my graph:
>
>     @prefix ex: <http://example.org/ns#> .
>     @prefix schema: <http://schema.org/> .
>
>     ex:Bob
>         a schema:Person ;
>     schema:review ex:BobsAggregateRating ;
>     .
>     ex:BobsAggregateRating
>         a schema:AggregateRating ;
>     schema:itemReviewed ex:Bob ;
>     .
>
>
>  1. When I take the schema:itemReviewed only out of
>     BobsAggregateRating, the validations passes for all three
>     xone/xor/or, which is correct.
>  2. When I take the schema:review only out of Bob, I
>     get sh:sourceConstraintComponent sh:XoneConstraintComponent
>     although I expect it to be valid by the first clause; when I use
>     sh:xor it works as expected and there is no violation
>  3. When I take out both properties, the validation passes with all of
>     sh:xone, sh:xor, and sh:or, although I expect a violation for the
>     missing schema:itemReviewed as per the first clause
>  4. When I leave them both in, I get two violations,
>     one sh:MaxCountConstraintComponent warning because of the second
>     clause, and, with sh:xone or sh:or, I get one generic sh:Violation
>     because none of clauses fit, which is perhaps expected since
>     sh:xone/sh:or only need one failure to satisfy, but when I use
>     sh:xor, I just get the one sh:MaxCountContraintComponent warning..
>
> Because of (1) and (4) it appears the (sh:not) sh:targetObjectOf is 
> working as a selector for each rule, but why do the other two cases 
> fail with sh:xone?  I am testing this using the shacl.org/playground 
> <http://shacl.org/playground>; I also tried this same pattern using 
> sh:or with the same results.
>
> What am I missing here?  Is this an appropriate use of 
> sh:xone/sh:xor/sh:or and/or sh:targetObjectOf?  sh:xor gets me three 
> out of the four cases as expected, but why would it fail (3)?
>
> Any and all guidance is most welcome :)
>
> -- 
> *Gary Murphy*
> Developer, Schema App
> e: gary@schemaapp.com <mailto:martha@schemaapp.com>
> w: https://www.schemaapp.com <https://www.schemaapp.com/>
>
Received on Saturday, 8 September 2018 01:02:47 UTC

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