- From: James Hudson <jameshudson3010@gmail.com>
- Date: Tue, 21 Apr 2020 14:37:36 -0400
- To: Irene Polikoff <irene@topquadrant.com>
- Cc: Public Shacl W3C <public-shacl@w3.org>
- Message-ID: <CAEUVO9H-FFZ7AOdKvyhjGxRcnXuabTRHF5ACKfQUVuf9N=1Q3A@mail.gmail.com>
Hello Irene,
I neglected to add:
Yes, the target picks every resource that is a subject of a triple. This is
what I want.
I also want to make sure that every subject has a property path that
terminates in a rdf:type of either rdfs:Class or rdf:Property.
To account for subjects like hr:missing, I believe that sh:path
[sh:zeroOrMorePath rdf:type] ; is what I should be using. This does result
in a validation error for hr:missing.
However, when using sh:path [sh:zeroOrMorePath rdf:type] ;, hr:Employee
produces a validation error because SHACL does not look at what the
rdf:type of hr:Employee is. I believe this is because of the zero part of
sh:zeroOrMorePath. When looking at hr:Employee, it only checks to see if
hr:Employee is either a rdfs:Class or rdf:Property and, because it is not,
it generates a validation error.
Using sh:path ( rdf:type rdf:type ) ; or sh:path ( rdf:type
[sh:zeroOrMorePath rdf:type] ) or sh:path ( rdf:type [sh:oneOrMorePath
rdf:type] ) does not result in a validation error for hr:missing.
Regards,
James
On Tue, Apr 21, 2020 at 2:11 PM Irene Polikoff <irene@topquadrant.com>
wrote:
> 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#> .
> @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 ( 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):
> 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>
> 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
>>
>> On Apr 21, 2020, at 12:56 PM, James Hudson <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#> .
>> @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
>>>
>>>
>>>
>>>
>>>
>>
>
Received on Tuesday, 21 April 2020 18:38:02 UTC