Re: Understanding Node vs Property Shapes and Property Paths

Hello Irene,

Thank you for your quickly reply.

If I try:

@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .
@prefix rdf:  <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
@prefix sch:  <http://schema.org/> .
@prefix sh:   <http://www.w3.org/ns/shacl#> .
@prefix ex:  <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):
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>
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>
> 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
>
> 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#> .
> @prefix rdf:  <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
> @prefix sch:  <http://schema.org/> .
> @prefix sh:   <http://www.w3.org/ns/shacl#> .
> @prefix ex:   <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):
> 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):
> 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
>
>
>
>
>