On 2021-12-20 10:22 pm, olidru wrote:
Thanks for you quick reply. The result of my SPARQL query describes
the violation. So, with your proposal the not existing part of the
triples is declared as violation.
What makes me wonder is that in opposite the expressions in
sh:property doesn’t describe the violation. What’s the reason for this
different understanding?
In all cases, the sh:condition shape describes the constraints that the
target nodes must fulfill. In the case of property constraints this is
quite intuitive, so if you say sh:hasValue :Value_1 then it will only
apply to nodes where that property has the given value. With
SHACL-SPARQL constraints, you formulate the constraints in a way that
may be confusing at first, because you have to state the patterns that
are *not* supposed to exist. So if the SPARQL query returns no result
(rows) then all is fine and the rule will fire. The reason for this
design is that this enables SPARQL queries to return more information
about the violation, e.g. the focus node (?this) and the value node
(?value).
Is this clearer now?
Holger
Many thanks for your help!
Oliver
On Monday, 20 December 2021 at 09:39:37 UTC+1 Holger Knublauch wrote:
Thanks for sending the details in a minimal executable format.
Made it much easier to play around.
The issue is that the sh:condition must apply to the focus
node(s), which means that before a rule is applied, the focus node
must not violate any constraints from the node shape that is the
sh:condition. In your example, the sh:sparql constraint will be
violated, because
PREFIX : <http://example.org/ex#> <http://example.org/ex#>
SELECT $this
WHERE {
$this :MyObjProp ?prop .
}
in SHACL means that it will produce a constraint violation for
each result in the SELECT query. In your example data, it would
produce one violation for each value of MyObjProp, of which there
are plenty.
Maybe you meant to say WHERE { FILTER NOT EXISTS { $this
:MyObjProp ?anyProp } } instead, to check that the focus node has
*no* value for that property?
HTH
Holger
On 2021-12-20 5:25 pm, olidru wrote:
The example ontology has two classes (:MyClass and :Value) and
two properties (:MyObjProp and:MyDataProp).
:MyClass
a owl:Class ;
a sh:NodeShape ;
rdfs:subClassOf owl:Thing ;
.
:MyDataProp
a owl:DatatypeProperty ;
rdfs:domain :MyClass ;
rdfs:range xsd:string ;
.
:MyObjProp
a owl:ObjectProperty ;
rdfs:domain :MyClass ;
rdfs:range :Value ;
.
:Value
a owl:Class ;
rdfs:subClassOf owl:Thing ; .
Some instances were added.
:MyClass_1
a :MyClass ;
:MyDataProp :Value_1 ;
:MyObjProp :Value_1 ; .
:MyClass_2 a :MyClass ;
:MyObjProp :Value_2 ;
.
:Value_1
a :Value ;
.
:Value_2
a :Value ;
.
A NodeShape :NodeShapeRule with a sh:rule (:SPARQLRule_1) was
created. This rule creates new triples. With the sh:condition the
rule should be restricted to a subset of targets.
:NodeShapeRule
a sh:NodeShape ;
sh:rule :SPARQLRule_1 ;
sh:targetClass :MyClass ;
.
:SPARQLRule_1
a sh:SPARQLRule ;
sh:condition :NodeShapeConditionSPARQL ;
sh:construct """
PREFIX : <http://example.org/ex#> <http://example.org/ex#>
CONSTRUCT {
$this :MyDataProp \"New input\" .
}
WHERE {
$this :MyObjProp ?p .
}
""" ;
.
For the restriction two equivalent NodeShapes were defined. The
first constraint works with sh:property, the other uses sh:sparql.
:NodeShapeConditionProperty
a sh:NodeShape ;
sh:property [
sh:path :MyObjProp ;
sh:description "NodeShapeConditionProperty" ;
sh:hasValue :Value_1 ;
] ;
sh:targetClass :MyClass ;
.
:NodeShapeConditionSPARQL
a sh:NodeShape ;
sh:sparql [
sh:message "NodeShapeConditionSPARQL" ;
sh:prefixes <http://example.org/ex> <http://example.org/ex> ;
sh:select """
PREFIX : <http://example.org/ex#> <http://example.org/ex#>
SELECT $this
WHERE {
$this :MyObjProp ?prop .
}
""" ;
] ;
sh:targetClass :MyClass ;
.
While doing inferencing with Topbraid Composer I received
different results for both solutions. Only the solution with
sh:property provides the expected response. Please, can anyone
explain me this behavior?
:MyClass_1 :MyDataProp "New input"
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