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.
