Validation of sh:targetNode when the node is not present in the data

[danaivach]

Current Behavior

RDF4J SailRepositoryConnection throws a ShaclSailValidationException in connection.commit() when adding SHACL rules with sh:targetNode combined with sh:minCount>0 or with sh:hasValue.

Expected Behavior

I'm flagging it as a bug because I would expect that sh:targetNode is supported based on #1362 and #1574.

Steps To Reproduce

Code sample:

    String shaclRules = "@prefix sh: <http://www.w3.org/ns/shacl#> .\n" +
            "@prefix xsd: <http://www.w3.org/2001/XMLSchema#> .\n\n" +
            "<http://example.org/component/component-state-context>\n" +
            "                       a sh:PropertyShape;\n" +
            "                       sh:targetNode <http://example.org/component>;\n" +
            "                       sh:path <https://saref.etsi.org/core/hasState>;\n" +
            "                       sh:maxCount 1;\n" +
            "                       sh:minCount 1;\n" +
            "                       sh:hasValue \"ready\".";

    ShaclSail shaclSail = new ShaclSail(new MemoryStore());
    Repository repo = new SailRepository(shaclSail);

    try (RepositoryConnection connection = repo.getConnection()) {

      // add shapes
      connection.begin();
      connection.clear(RDF4J.SHACL_SHAPE_GRAPH);
      connection.add(new StringReader(shaclRules), "", RDFFormat.TURTLE, RDF4J.SHACL_SHAPE_GRAPH);
      connection.commit();

    } catch (IOException e) {
      throw new RuntimeException(e);
    }
 

Exception:

org.eclipse.rdf4j.sail.shacl.ShaclSailValidationException: Failed SHACL validation
org.eclipse.rdf4j.repository.RepositoryException: org.eclipse.rdf4j.sail.shacl.ShaclSailValidationException: Failed SHACL validation
	at org.eclipse.rdf4j.repository.sail.SailRepositoryConnection.commit(SailRepositoryConnection.java:228)
	at ch.unisg.ics.interactions.hmas.interaction.validation.ShaclValidationTest.testContextValidationRDF4j(ShaclValidationTest.java:178)
	at java.base/java.lang.reflect.Method.invoke(Method.java:580)
	at java.base/java.util.ArrayList.forEach(ArrayList.java:1596)
	at java.base/java.util.ArrayList.forEach(ArrayList.java:1596)
Caused by: org.eclipse.rdf4j.sail.shacl.ShaclSailValidationException: Failed SHACL validation
	at org.eclipse.rdf4j.sail.shacl.ShaclSailConnection.prepare(ShaclSailConnection.java:892)
	at org.eclipse.rdf4j.repository.sail.SailRepositoryConnection.commit(SailRepositoryConnection.java:225)

Version

5.0.2

Are you interested in contributing a solution yourself?

None

Anything else?

No response

[hmottestad]

Our implementation is based on the premise that a target node doesn't actually have to exist for it to violate a shape. In your case you are saying that <http://example.org/component> has to have at least one <https://saref.etsi.org/core/hasState> path when using sh:minCount 1.

I'll check the specification and test cases to see if this is the correct interpretation or not.

[hmottestad]

Seems that it’s correct to validate the minCount constraint for a targetNode even if the target node is not present in the data.

The spec isn't exactly very clear: https://www.w3.org/TR/shacl/#targetNode

But there is a test case that is validated against the reference SHACL implementation:

• https://github.com/eclipse-rdf4j/rdf4j/blob/main/core/sail/shacl/src/test/resources/test-cases/minCount/targetNode/shacl.trig
• https://github.com/eclipse-rdf4j/rdf4j/tree/main/core/sail/shacl/src/test/resources/test-cases/minCount/targetNode/invalid/case2

There is also a test from the W3C SHACL test suite that tests for something similar: https://github.com/eclipse-rdf4j/rdf4j/blob/main/core/sail/shacl/src/test/resources/w3c/core/node/datatype-002.ttl

An issue with that test though is that it doesn't seem to differentiate between what is data and what are shapes, so the nodes are definitely present in the data graph.

[danaivach]

Thank you. I had misinterpreted the role of the SHACL rules upon committing them, assuming that the rules will not be violated if the target node does not exist.

The ShaclSailValidationException is indeed not raised if the conforming node is added in the graph prior to the addition of the SHACL rules.