Hi Andy,
Thanks very much for the shacl guidance. The use of sh:targetSubjectsOf is
quite helpful. I replaced the bdo:personName w/ bdo:isRoot which must be
present on any Entity resource so that if a Work or Place or other entity is
checked it will fail if it isn’t a bdo:Person.
This still fails in the event that there is no bdo:isRoot so in some way that
negative needs also to be caught to weed out really malformed graphs.
I still have a question about the shacl endpoint:
Is the ?graph parameter validated in the context of the entire dataset
specified in the endpoint URL or just the named graph itself?
It appears to be just the named graph itself so is the same as running the
shacl command outside of Fuseki.
We are wanting a validation of the named graph against the entire (union)
dataset graph which will have sufficient information about subClassOf* and
external resources like P705 without entailing a validation of all nodes
reachable from triples in the ?graph named graph. This might be similar to:
validator.validate(shapes, dsg, node)
where node would be the root resource URI like,
<http://purl.bdrc.io/resource/P707 <http://purl.bdrc.io/resource/P707>>.
Is this something that needs an issue raised and a bit of extension of the
endpoint or is there another way to get this kind of behavior through the
endpoint?
Thank you very much for your help,
Chris
> On May 13, 2020, at 12:16 PM, Andy Seaborne <a...@apache.org> wrote:
>
>
>
> On 13/05/2020 16:03, Chris Tomlinson wrote:
>> Hi Andy,
>> Thank you for the reply. I can get your example to work as you indicate, but
>> have some questions:
>> 1) I went through the latest SHACL draft
>> <https://w3c.github.io/data-shapes/shacl/> and I cannot find how to know
>> that sh:targetNode always executes. It’s also not clear to me what it means
>> to execute. I thought that sh:targetNode X was a way to restrict a shape to
>> X in the data graph, whatever X might be.
>
> It sets the target node to X and that becomes $this.
>
> It does not say the target has to be in the graph.
>
> The tests use this idiom quite a lot.
>
> This matters because in some places the spec is not complete and without some
> light reverse engineering from the tests, I'd not have been able to implement
> some of the SPARQL functionality (particularly SPARQL components, not the
> SPARQl constraints we're talking about here).
>
> Also, RDF graphs do not have a formally defined set of nodes - they are a set
> of edges and any nodes you want can be used in triples.
>
>> 2) What I’m trying to do is validate that a resource like
>> http://purl.bdrc.io/resource/P707 <http://purl.bdrc.io/resource/P707> is a
>> Person, which at a minimum means that:
>> <http://purl.bdrc.io/resource/P707 <http://purl.bdrc.io/resource/P707>>
>> a <http://purl.bdrc.io/ontology/core/Person
>> <http://purl.bdrc.io/ontology/core/Person>> .
>> is present in the http://purl.bdrc.io/graph/P707
>> <http://purl.bdrc.io/graph/P707>. The PersonShape
>> <https://github.com/buda-base/editor-templates/blob/master/templates/core/person.shapes.ttl>
>> has:
>> sh:targetClass bdo:Person
>> but that only serves to say that PersonShape only applies to resources of
>> class bdo:Person and if there are none, then there are no violations which
>> means I can try to validate a bibliographic element such as
>> http://purl.bdrc.io/resource/W1FPL1 <http://purl.bdrc.io/resource/W1FPL1>
>> which is of class bdo: ImageInstance but of course that still sh:conforms
>> true since bds:PersonShape doesn’t apply and hence there aren’t any
>> violations. (to see the resources, use
>> http://ldspdi-dev.bdrc.io/resource/W1FPL1.ttl
>> <http://ldspdi-dev.bdrc.io/resource/W1FPL1.ttl>, for example).
>> The use case is: a client submits a graph of a resource and claims it to be
>> a bdo:Person or a subClassOf* it; and we want to validate the graph as a
>> bdo:Person and so want to get the result “false" for bdr:W1FPL1 instead of
>> “true".
>> It’s our intent to use a tool like shacl for this top-level task as well as
>> validating the details liuke having at least one name, a gender, and so on.
>> I tried using something like your example:
>> bds:CheckPersonClassShape a sh:NodeShape ;
>> rdfs:label "Check Person Class Shape"@en ;
>> sh:targetNode "Check Class" ;
>> sh:sparql [
>> a sh:SPARQLConstraint ;
>> sh:prefixes [
>> sh:declare [
>> sh:prefix "rdf" ;
>> sh:namespace "http://www.w3.org/1999/02/22-rdf-syntax-ns#"; ;
>> ] , [
>> sh:prefix "bdo" ;
>> sh:namespace "http://purl.bdrc.io/ontology/core/"; ;
>> ]
>> ] ;
>> sh:select """
>> select $this (rdf:type as ?path) (bdo:Person as ?value)
>> where {
>> filter not exists { $this ?path ?value }
>> }
>> """ ;
>
> That query does not look right.
>
> 1/ $this is the targetNode
>
> $this is "Check Class" - the shape needs to find the thing that is the person
> amongst the several subjects in the data. That can be in the SPARQL or as a
> target of some kind.
>
> Either set the target to be bdr:P707
> or find a signature such has a bdo:personName triple. "sh:targetSubjectsOf
> bdo:personName"
> or write some pattern in the SPARQL query.
>
> You may want some "whole graph" validation such as not completely empty or
> has at least some relevant vocabulary to ensure that the data is not so off
> that nothing will trigger. That's where the sh:targetNode "foobar" trick
> comes in.
>
> 2/ It's looking for any triple with $this as subject, not "a bdo:Person"
>
> The SELECT-AS happens after the WHERE.
> FILTER NOT EXISTS does not set ?path ?value so if they are unset there are
> free variables.
>
> filter not exists { $this ?P ?O }
>
> would be just the same and matches any triple with $this as subject.
>
>
>
> You want to set ?value and ?path before the FILTER:
>
> BIND (bdo:Person as ?value)
> BIND (rdf:type as ?path)
>
>
>
> or write directly and not worry about ?path and ?value.
>
> filter not exists { $this rdf:type bdo:Person }
>
> (
> The message processing from SPARQL constraints and components doesn't do
> templating.
> )
>
>> ] ;
>> .
>> But this just always reports a violation that the literal, “Check Class”,
>> doesn’t conform, which is true since it isn’t in the data graph.
>
>
> bds:CheckPersonClassShape a sh:NodeShape ;
> rdfs:label "Check Person Class Shape"@en ;
> ## sh:targetNode bdr:P707 ;
> sh:targetSubjectsOf bdo:personName ;
> sh:sparql [
> a sh:SPARQLConstraint ;
> sh:prefixes [
> sh:declare [
> sh:prefix "rdf" ;
> sh:namespace "http://www.w3.org/1999/02/22-rdf-syntax-ns#"; ;
> ] , [
> sh:prefix "bdo" ;
> sh:namespace "http://purl.bdrc.io/ontology/core/"; ;
> ]
> ] ;
> sh:select """
> select $this
> where {
> filter not exists { $this rdf:type bdo:Person }
> }
> """ ;
> ] ;
> .
>
>
>
> shacl validate -v -s shapes.ttl -d P707.ttl
>
> shows the validation when "a bdo:Person ;" commented out of the data:
>
> NodeShape[http://example/CheckPersonClassShape]
> N: FocusNodes(1): [http://purl.bdrc.io/resource/P707]
> F: http://purl.bdrc.io/resource/P707
> S: NodeShape[http://example/CheckPersonClassShape]
> C: SPARQL[PREFIX bdo: <http://purl.bdrc.io/ontology/core/> PREFIX rdf:
> <http://www.w3.org/1999/02/22-rdf-syntax-ns#> SELECT ?this WHERE { FILTER
> NOT EXISTS { ?this rdf:type bdo:Person } }]
>
> ... prefixes ...
>
> [ a sh:ValidationReport ;
> sh:conforms false ;
> sh:result [ a sh:ValidationResult ;
> sh:focusNode bdr:P707 ;
> sh:resultMessage "SPARQL SELECT constraint for
> <http://purl.bdrc.io/resource/P707> returns
> <http://purl.bdrc.io/resource/P707>" ;
> sh:resultSeverity sh:Violation ;
> sh:sourceConstraintComponent sh:SPARQLConstraintComponent ;
> sh:sourceShape bds:CheckPersonClassShape ;
> sh:value bdr:P707
> ]
> ] .
>
>
>> 3) The original reason for wanting to use the shacl endpoint was so that we
>> could PUT the submitted graph in the Fuseki dataset and then use the
>> endpoint to validate the resource bdr:P707 (or bdr:W1FPL1) as a Person (or
>> not) with the rest of the dataset graph available to handle things like
>> subClassOf* and subPropertyOf* for various items as well as validating the
>> minimum of resources referenced by P707 such as that P705 is a male person
>> and hence can be a father of P707.
>
> That sounds like
>
> sh:targetNode bdr:P707
>
> and also some shapes to check "is there anything relevant at all".
>
> Andy
>
>> The graph for P707 that is submitted would only have references to P705,
>> with no properties on P705, since that resource is in its own graph.
>> I thought this is pretty much how validate(Shapes Graph, Node) would work,
>> where Graph would be the union dataset graph.
>> I’m evidently missing some understanding.
>> I appreciate your patience,
>> Chris
>>> On May 12, 2020, at 3:52 AM, Andy Seaborne <a...@apache.org> wrote:
>>>
>>> Chris,
>>>
>>> Here's a shape that always executes and tests for an empty data graph.
>>>
>>> # No violation
>>> shacl validate -v -shapes ex-shapes.ttl -data not-empty.ttl
>>>
>>> # Violation
>>> shacl validate -v -shapes ex-shapes.ttl -data empty.nt
>>>
>>> "sh:targetNode" always executes.
>>>
>>> With this pattern, the SPARQL query can do arbitrary checks.
>>>
>>> Andy
>>>
>>> ## ex-shapes.ttl
>>> PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
>>> PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
>>>
>>> PREFIX sh: <http://www.w3.org/ns/shacl#>
>>> PREFIX xsd: <http://www.w3.org/2001/XMLSchema#>
>>>
>>> PREFIX ex: <http://example/>
>>>
>>> ex:NotEmptyGraphShape
>>> rdf:type sh:NodeShape ;
>>> sh:targetNode "Empty Graph" ;
>>> sh:sparql [
>>> a sh:SPARQLConstraint ;
>>> sh:select """
>>> SELECT $this ?value
>>> WHERE {
>>> FILTER NOT EXISTS { ?s ?p ?o }
>>> }
>>> """ ;
>>> ] .
>>>
>>> On 11/05/2020 17:14, Chris Tomlinson wrote:
>>>
>>>> I appreciate that it works that way but until and unless I can understand
>>>> your point about
>>>> [] sh:targetNode ex:myNode
>>>> then I don’t know how to distinguish: 1) no violations because a Person
>>>> graph conforms to the PersonShapes - like there’s no Work indicated as a
>>>> parent of the person or a rdfs:label is used where a skos:prefLabel is
>>>> expected; versus 2) no violations because the question is vacuous like
>>>> asking if a Work looks like a person or an empty non-existent graph looks
>>>> like a person.
