A simple SPIN rule doesn't work in RDF4J

Question

I've just started using the triple store RDF4J (I am using its workbench, version 2.3.1, run on Windows 10 with Tomcat 9.0)

I want to use the SPIN rules in RDF4J. Therefore, I created a new repository (In memory with RDFS+SPIN support).

I wanted to start with the SPIN example in RDF4J documentation concerning how to add SPIN rules. That is, I added the data (in Turtle, and imported to RDF4J)

@prefix ex: <http://example.org/>.
        ex:John a ex:Father ;
ex:parentOf ex:Lucy .
ex:Lucy a ex:Person .

And the rule:

@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>.
@prefix sp: <http://spinrdf.org/sp#>.
@prefix spin: <http://spinrdf.org/spin#>.
@prefix ex: <http://example.org/>.
ex:Person a rdfs:Class ;
    spin:rule [
        a sp:Construct ;
    sp:text """PREFIX ex: <http://example.org/>
               CONSTRUCT { ?this ex:childOf ?parent . }
               WHERE { ?parent ex:parentOf ?this . }"""
] .

And as instructed in the documentation, I exposed the query (with the checkbox 'Include inferred statements' checked),

PREFIX ex: <http://example.org/>
SELECT ?child 
WHERE { ?child ex:childOf ?parent }

However, no result returned:

Could someone, please tell me am I doing something wrong, why the SPIN rule doesn't work in my RDF4J workbench, have I missed something?

Answer 1

(reposting my comment as an answer for future readers)

The SPIN reasoner currently assumes that all data is in the default context, I think. Make sure that your data was not added to a named graph.