How to get a collection of classes from Bnode

[cory1219]

Hello,

My owl file has a triple as below. When I import the file, the object of the triple becoems rdflib.term.bnode. How can I get the class names of the object in the collection, namely Entity & Resource? Thanks

<owl:ObjectProperty rdf:about="http://www.semanticweb.org/xxx/ontologies/2020/SimulationOntology#isPerformedOn">
        <rdfs:domain rdf:resource="http://www.semanticweb.org/xxx/ontologies/2020/SimulationOntology#Activity"/>
        <rdfs:range>
            <owl:Class>
                <owl:unionOf rdf:parseType="Collection">
                    <rdf:Description rdf:about="http://www.semanticweb.org/xxx/ontologies/2020/SimulationOntology#Entity"/>
                    <rdf:Description rdf:about="http://www.semanticweb.org/xxx/ontologies/2020/SimulationOntology#Resource"/>
                </owl:unionOf>
            </owl:Class>
        </rdfs:range>
    </owl:ObjectProperty>

[kouralex]

I had a bit similar use case. After a while, I found it easier to just SPARQL the results via a specifically crafted query. To achieve this, I used rdflib.plugins.sparql.processor.prepareQuery() like this:

preparedQuery = prepareQuery(
    'SELECT ?s ?p WHERE { ?s ?p ?o . ?o owl:unionOf ?o2 . ?o2 rdf:rest*/rdf:first ?o3 .}',
    initNs = { 'owl': OWL, 'rdf': RDF }
 )

and used it like this (as I had ?o3 fixed and was interested in ?s and ?p):

for s, p in graph.query(preparedQuery, initBindings={'o3', o}:
    # Do whatever you need

In your case you could probably just fix ?s and maybe even ?p and get the results you wanted.

However, there may be some penalty in performing such a query instead of just navigating the graph using the plain old methods designed for that but as it appeared to me, it was much more cumbersome or maybe I just missed some obvious way to do it.