Re: Understanding Node vs Property Shapes and Property Paths

Well, your target picks every resource that is a subject of a triple. I thought you wanted to make sure that they all have types. Since hr:missing does not have a type, you get a violation. That seems correct to me.

If you simply wanted to say that any object in a triple with rdf:type predicate must itself have a type, then you do not need SPARQL based target. You could simply use sh:targetObjectsOf rdf:type.

> On Apr 21, 2020, at 1:39 PM, James Hudson <jameshudson3010@gmail.com> wrote:
> 
> Hello Irene,
> 
> Unfortunately, sh:path (rdf:type rdf:type); validates:
> 
> hr:missing rdfs:comment "some comment about missing" .
> 
> which does not have any value of rdf:type. This focus node should produce a validation error.
> 
> I also believe that I would actually want ( rdf:type [sh:oneOrMorePath rdf:type] ) ;  as the chain could be longer then just two. However, this does not resolve the problems.
> 
> I tried:
> 
> @prefix rdfs: <http://www.w3.org/2000/01/rdf-schema# <http://www.w3.org/2000/01/rdf-schema#>> .
> @prefix rdf:  <http://www.w3.org/1999/02/22-rdf-syntax-ns# <http://www.w3.org/1999/02/22-rdf-syntax-ns#>> .
> @prefix sch:  <http://schema.org/ <http://schema.org/>> .
> @prefix sh:   <http://www.w3.org/ns/shacl# <http://www.w3.org/ns/shacl#>> .
> @prefix ex:  <http://example.org/ <http://example.org/>> .
> 
> ex:ClassOrProperty
>     a sh:PropertyShape ;
>     sh:target [
>         a sh:SPARQLTarget ;
>         sh:select   """
>                     SELECT ?this
>                     WHERE {
>                         ?this ?p ?o .
>                     }
>                     """ ;
>     ] ;
> 
> 
>     sh:path     ( rdf:type [sh:oneOrMorePath rdf:type] ) ;
>     sh:in       ( rdfs:Class rdf:Property ) ;
>     sh:maxCount 1 ;                 # path-maxCount
>     sh:minCount 1 ;                 # PropertyShape-path-minCount
> 
> .
> 
> Hoping that I could say to validate where the property path terminates and that it has to contain at least one value found in sh:in, but this produced the unwanted validation error:
> 
> Constraint Violation in MinCountConstraintComponent (http://www.w3.org/ns/shacl#MinCountConstraintComponent <http://www.w3.org/ns/shacl#MinCountConstraintComponent>):
>  Severity: sh:Violation
>  Source Shape: ex:ClassOrProperty
>  Focus Node: hr:Employee
>  Result Path: ( rdf:type rdf:type )
> 
> The only thing I need to be able to do is to validate where the property path terminates and that does not seem possible with SHACL. Based on that, I have to believe that my sh:path should be sh:path [sh:zeroOrMorePath rdf:type] ; to account for focus nodes which do not have a rdf:type defined. Unfortunately, SHACL requires that every node along a path be validated with the same test and cannot just validate where the property path terminates.
> 
> Regards,
> James
> 
> 
> On Tue, Apr 21, 2020 at 1:18 PM Irene Polikoff <irene@topquadrant.com <mailto:irene@topquadrant.com>> wrote:
> No, I meant sequence path without any zero or more or one or more. Simply rdf:type/rdf:type as opposed to rdf:type+/rdf:type which doesn’t make much sense.
> 
> sh:path (rdf:type rdf:type);
> 
> See https://www.w3.org/TR/shacl/#property-paths <https://www.w3.org/TR/shacl/#property-paths>
> 
>> On Apr 21, 2020, at 12:56 PM, James Hudson <jameshudson3010@gmail.com <mailto:jameshudson3010@gmail.com>> wrote:
>> 
>> Hello Irene,
>> 
>> Thank you for your quickly reply.
>> 
>> If I try:
>> 
>> @prefix rdfs: <http://www.w3.org/2000/01/rdf-schema# <http://www.w3.org/2000/01/rdf-schema#>> .
>> @prefix rdf:  <http://www.w3.org/1999/02/22-rdf-syntax-ns# <http://www.w3.org/1999/02/22-rdf-syntax-ns#>> .
>> @prefix sch:  <http://schema.org/ <http://schema.org/>> .
>> @prefix sh:   <http://www.w3.org/ns/shacl# <http://www.w3.org/ns/shacl#>> .
>> @prefix ex:  <http://example.org/ <http://example.org/>> .
>> 
>> ex:ClassOrProperty
>>     a sh:PropertyShape ;
>>     sh:target [
>>         a sh:SPARQLTarget ;
>>         sh:select   """
>>                     SELECT ?this
>>                     WHERE {
>>                         ?this ?p ?o .
>>                     }
>>                     """ ;
>>     ] ;
>> 
>> 
>>     sh:path     ( [sh:zeroOrMorePath rdf:type] rdf:type ) ;
>>     sh:in       ( rdfs:Class rdf:Property ) ;
>> .
>> 
>> which is what I think you mean by "rdf:type/rdf:type as the path", I still get the following unexpected validation error:
>> 
>> Constraint Violation in InConstraintComponent (http://www.w3.org/ns/shacl#InConstraintComponent <http://www.w3.org/ns/shacl#InConstraintComponent>):
>>  Severity: sh:Violation
>>  Source Shape: ex:ClassOrProperty
>>  Focus Node: hr:Longer
>>  Value Node: hr:Employee
>>  Result Path: ( [ sh:zeroOrMorePath rdf:type ] rdf:type )
>> 
>> By unexpected, I mean I do not want it to be considered a validation error because the rdf:type property path terminates at rdfs:Class.
>> 
>> When you say "zero or more paths will deliver values hr:Long, hr:Employee, rdfs:Class," does that mean that the sh:in test will be performed on the value of hr:Long (fail), hr:Employee (fail), and rdfs:Class (pass)? Is it possible to have it validate only where the property path terminates?
>> 
>> Regards,
>> James
>> 
>> On Tue, Apr 21, 2020 at 12:12 PM Irene Polikoff <irene@topquadrant.com <mailto:irene@topquadrant.com>> wrote:
>> This looks correct.
>> 
>> With data:
>> 
>> hr:Long a hr:Employee.
>> hr:Employee a rdfs:Class.
>> 
>> If your focus node is hr:Long, zero or more paths will deliver values hr:Long, hr:Employee, rdfs:Class. One or more paths will deliver values  hr:Employee, rdfs:Class.
>> 
>> You could try rdf:type/rdf:type as the path. This will get the type of a resource that is used as a type and ensure that it is rdfs:CLass or rdf:Property.
>> 
>>> On Apr 21, 2020, at 11:39 AM, James Hudson <jameshudson3010@gmail.com <mailto:jameshudson3010@gmail.com>> wrote:
>>> 
>>> Hello,
>>> 
>>> Since people here have been so helpful in the past, I thought I would ask a few more questions.
>>> 
>>> Background to this is my SO question at https://stackoverflow.com/questions/61323857/what-is-the-difference-between-these-shape-graphs-which-use-shor <https://stackoverflow.com/questions/61323857/what-is-the-difference-between-these-shape-graphs-which-use-shor>
>>> 
>>> The SO question has the data graph under consideration.
>>> 
>>> In the book Validating RDF, it says:
>>> 
>>> Node shapes declare constraints directly on a node. Property shapes declare constraints on the values associated with a node through a path.
>>> 
>>> Based on this, I believe I want to use a Property Shape because I want to define a constraint on the value of the rdf:type path on a focus node. Is this correct?
>>> 
>>> If I try the property shape:
>>> 
>>> @prefix rdfs: <http://www.w3.org/2000/01/rdf-schema# <http://www.w3.org/2000/01/rdf-schema#>> .
>>> @prefix rdf:  <http://www.w3.org/1999/02/22-rdf-syntax-ns# <http://www.w3.org/1999/02/22-rdf-syntax-ns#>> .
>>> @prefix sch:  <http://schema.org/ <http://schema.org/>> .
>>> @prefix sh:   <http://www.w3.org/ns/shacl# <http://www.w3.org/ns/shacl#>> .
>>> @prefix ex:   <http://example.org/ <http://example.org/>> .
>>> 
>>> ex:ClassOrProperty
>>>     a sh:PropertyShape ;
>>>     sh:target [
>>>         a sh:SPARQLTarget ;
>>>         sh:select   """
>>>                     SELECT ?this
>>>                     WHERE {
>>>                         ?this ?p ?o .
>>>                     }
>>>                     """ ;
>>>     ] ;
>>> 
>>> 
>>>     sh:path [sh:zeroOrMorePath rdf:type] ;
>>>     sh:in ( rdfs:Class rdf:Property ) ;
>>> .
>>> 
>>> I get the unexpected validation error:
>>> (J)
>>> Constraint Violation in InConstraintComponent (http://www.w3.org/ns/shacl#InConstraintComponent <http://www.w3.org/ns/shacl#InConstraintComponent>):
>>>  Severity: sh:Violation
>>>  Source Shape: ex:ClassOrProperty
>>>  Focus Node: hr:Longer
>>>  Value Node: hr:Employee
>>>  Result Path: [ sh:zeroOrMorePath rdf:type ]
>>> 
>>> The way I thought [sh:zeroOrMorePath rdf:type] ; would work is that it would consider the node hr:Longer and follow the rdf:type path through hr:Employee to where it terminates at rdfs:Class and then validate. However, it seems to stop one step away, sees that hr:Employee is not a rdfs:Class or rdf:Property and then generates a validation error.
>>> 
>>> I get another unexpected validation error:
>>> (K)
>>> Constraint Violation in InConstraintComponent (http://www.w3.org/ns/shacl#InConstraintComponent <http://www.w3.org/ns/shacl#InConstraintComponent>):
>>>  Severity: sh:Violation
>>>  Source Shape: ex:ClassOrProperty
>>>  Focus Node: hr:Employee
>>>  Value Node: hr:Employee
>>>  Result Path: [ sh:zeroOrMorePath rdf:type ]
>>> 
>>> I was thinking that the zero in sh:zeroOrMorePath would see hr:Employee a rdfs:Class ; and validate. Is it the case that the zero in sh:zeroOrMorePath causes a validation engine to compare a node against itself without following or looking for the path?
>>> 
>>> I did try using sh:oneOrMorePath, but I received the validation error (J) again, but (K) did not show up. Is the reason why (K) did not show up because it was forced to see hr:Employee a rdfs:Class ; because of the one in sh:oneOrMorePath and could validate it?
>>> 
>>> Perhaps a validation engine validates every node along the path and not just where the path terminates? If this is the case, is it possible to validate where the path terminates only?
>>> 
>>> Needless to say, I am rather confused.
>>> 
>>> Can anyone clear this up?
>>> 
>>> Thank you,
>>> James
>>> 
>>> 
>>> 
>> 
> 

Received on Tuesday, 21 April 2020 18:12:00 UTC