- From: Irene Polikoff <irene@topquadrant.com>
- Date: Tue, 21 Apr 2020 15:12:17 -0400
- To: James Hudson <jameshudson3010@gmail.com>
- Cc: Public Shacl W3C <public-shacl@w3.org>
- Message-Id: <75F20793-6818-48E3-84AA-0813686E9650@topquadrant.com>
> On Apr 21, 2020, at 2:37 PM, James Hudson <jameshudson3010@gmail.com> wrote: > > 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. What path? Saying that a path terminates in something does not specify a path. It is either 1. You require every resource that is a subject of any triples to have rdf:type that is either a class or a property. In which case hr:missing is correctly identified as missing a type OR 2. You require that every resource that is used as a value of rdf:type has a type that is either a class or a property. In which case, use sh:targetObjectsOf rdf:type OR 3. You want to ensure that some resources have a type that is a class or a property. It is not clear to me which resources they are. If you know what your criteria is, what resources you want to exclude and include, then it can be defined. > > 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. This means ?s rdf:type+ ?type which when hr:Long is bound to ?s will return hr:Long, hr:Employee and rdfs:Class. All of these values will be validated against the constraint and hr:Long gives you an error because its type is not rdfs:Class. It is hr:Employee. SHACL paths are the same as SPARQL paths https://www.w3.org/TR/sparql11-property-paths/ <https://www.w3.org/TR/sparql11-property-paths/>. > > > 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 <mailto: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 <mailto: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 19:12:33 UTC