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.
