How to get complete info on all subclass assertions for a given class?

[Jos Lehmann]

Hi there

I would like to list subclass assertions *completely*, i.e., also including object properties with their restrictions.

At the moment I am getting a mixed bag:

- Subclass assertions proper return output like [1] or [2] in MY OUTPUT below (*that's OK*);

- Subclass assertions that use anonymous classes (i.e. a property + restriction + range) return output like [3] in MY OUTPUT below (*not OK*);

How should I change MY CODE below to see what's inside -7d9d6f3d:15a658d8bb4:-7f27 (in terms of object property, restriction and range of restriction for the particular class at hand) ?


Thanks, Jos


MY CODE

ExtendedIterator classes = model.listClasses();
while (classes.hasNext()) {
OntClass thisClass = (OntClass) classes.next();
ExtendedIterator properties = thisClass.listProperties();
while (properties.hasNext()){
Statement thisProperty = (Statement) properties.next();
if (thisProperty.getPredicate().toString().contains("sub")) {
System.out.println("Contains sub_P: " + thisProperty.getPredicate() + " Contains sub_O: " + thisProperty.getObject());
}

}
}


MY OUTPUT

[1] Contains sub_P: http://www.w3.org/2000/01/rdf-schema#subClassOf Contains sub_O: http://www.bauhaus-luftfahrt.net/ontologies/2016/Ls_Ontology.owl#XXX
[2] Contains sub_P: http://www.w3.org/2000/01/rdf-schema#subClassOf Contains sub_O: http://www.bauhaus-luftfahrt.net/ontologies/2016/Ls_Ontology.owl#YYY
[3] Contains sub_P: http://www.w3.org/2000/01/rdf-schema#subClassO

[Lorenz B.]

Jena is primarily an RDF library, thus, it's working on the concept of
nodes and triples.

The RDF-based notation of OWL axioms and also OWL class expressions can
be found here [1] . You can see that n triples encode on OWL construct,
thus, blank nodes are used as you already discovered. For example, the
encoding of the existential restriction (:hasAuthor some :Author) would
be similar to

_:x rdf:type owl:Restriction .
_:x owl:onProperty :hasAuthor .
_:x owl:someValuesFrom :Author .


The problem now is, that for instance OWL class expression can be
arbitrarily deep nested which makes the corresponding RDF even more complex.
Of course, if you know that superclasses follow a particular
schema/template, then you could resolve the blank nodes and get it's
triples.

In your example you could ask for all outgoing statements of the object
node, e.g.

model.listStatements(thisProperty.getObject(), null, (RDFNode)
null); // untested!

For the "author" example, you should get the statements back.
Note that if the superclass is more complex, this would have to be done
recursively for each blank node that occurs in object position


Nevertheless, the ontology layer of Jena has some support for OWL 1
complex classes and restrictions [2] . Having a more deep look at the
OntClass [3], there is a method asRestriction() which could be used to
cast the object to a Restriction object [4] which itself has a bunch of
methods to check for/convert to the corresponding type of restriction.
Maybe this is already enough for you, otherwise I think Dave Reynolds is
the developer of the ontology layer, so he'll probably give you a better
answer.



[1] https://www.w3.org/TR/owl2-mapping-to-rdf/
[2]
https://jena.apache.org/documentation/ontology/#more-complex-class-expressions
[3]
https://jena.apache.org/documentation/javadoc/jena/org/apache/jena/ontology/OntClass.html
[4]
https://jena.apache.org/documentation/javadoc/jena/org/apache/jena/ontology/Restriction.html


Cheers,
Lorenz

Post by Jos Lehmann
Hi there
I would like to list subclass assertions *completely*, i.e., also including object properties with their restrictions.
- Subclass assertions proper return output like [1] or [2] in MY OUTPUT below (*that's OK*);
- Subclass assertions that use anonymous classes (i.e. a property + restriction + range) return output like [3] in MY OUTPUT below (*not OK*);
How should I change MY CODE below to see what's inside -7d9d6f3d:15a658d8bb4:-7f27 (in terms of object property, restriction and range of restriction for the particular class at hand) ?
Thanks, Jos
MY CODE
ExtendedIterator classes = model.listClasses();
while (classes.hasNext()) {
OntClass thisClass = (OntClass) classes.next();
ExtendedIterator properties = thisClass.listProperties();
while (properties.hasNext()){
Statement thisProperty = (Statement) properties.next();
if (thisProperty.getPredicate().toString().contains("sub")) {
System.out.println("Contains sub_P: " + thisProperty.getPredicate() + " Contains sub_O: " + thisProperty.getObject());
}
}
}
MY OUTPUT
[1] Contains sub_P: http://www.w3.org/2000/01/rdf-schema#subClassOf Contains sub_O: http://www.bauhaus-luftfahrt.net/ontologies/2016/Ls_Ontology.owl#XXX
[2] Contains sub_P: http://www.w3.org/2000/01/rdf-schema#subClassOf Contains sub_O: http://www.bauhaus-luftfahrt.net/ontologies/2016/Ls_Ontology.owl#YYY
[3] Contains sub_P: http://www.w3.org/2000/01/rdf-schema#subClassOf Contains sub_O: -7d9d6f3d:15a658d8bb4:-7f27

[Jos Lehmann]

Hi Lorenz

As I am working with a fairly predictable ontology, I did not need full recursion and managed to get my result with adapted and nested calls to:

model.listStatements(thisProperty.getObject(), null, (RDFNode) null);

Thanks for the help, Jos


-----Ursprüngliche Nachricht-----
Von: Lorenz B. [mailto:***@informatik.uni-leipzig.de]
Gesendet: Donnerstag, 23. Februar 2017 09:05
An: ***@jena.apache.org
Betreff: Re: How to get complete info on all subclass assertions for a given class?

Jena is primarily an RDF library, thus, it's working on the concept of nodes and triples.

The RDF-based notation of OWL axioms and also OWL class expressions can be found here [1] . You can see that n triples encode on OWL construct, thus, blank nodes are used as you already discovered. For example, the encoding of the existential restriction (:hasAuthor some :Author) would be similar to

_:x rdf:type owl:Restriction .
_:x owl:onProperty :hasAuthor .
_:x owl:someValuesFrom :Author .


The problem now is, that for instance OWL class expression can be arbitrarily deep nested which makes the corresponding RDF even more complex.
Of course, if you know that superclasses follow a particular schema/template, then you could resolve the blank nodes and get it's triples.

In your example you could ask for all outgoing statements of the object node, e.g.

model.listStatements(thisProperty.getObject(), null, (RDFNode)
null); // untested!

For the "author" example, you should get the statements back.
Note that if the superclass is more complex, this would have to be done recursively for each blank node that occurs in object position


Nevertheless, the ontology layer of Jena has some support for OWL 1 complex classes and restrictions [2] . Having a more deep look at the OntClass [3], there is a method asRestriction() which could be used to cast the object to a Restriction object [4] which itself has a bunch of methods to check for/convert to the corresponding type of restriction.
Maybe this is already enough for you, otherwise I think Dave Reynolds is the developer of the ontology layer, so he'll probably give you a better answer.



[1] https://www.w3.org/TR/owl2-mapping-to-rdf/
[2]
https://jena.apache.org/documentation/ontology/#more-complex-class-expressions
[3]
https://jena.apache.org/documentation/javadoc/jena/org/apache/jena/ontology/OntClass.html
[4]
https://jena.apache.org/documentation/javadoc/jena/org/apache/jena/ontology/Restriction.html


Cheers,
Lorenz

Post by Jos Lehmann
Hi there
I would like to list subclass assertions *completely*, i.e., also including object properties with their restrictions.
- Subclass assertions proper return output like [1] or [2] in MY
OUTPUT below (*that's OK*);
- Subclass assertions that use anonymous classes (i.e. a property +
restriction + range) return output like [3] in MY OUTPUT below (*not
OK*);
How should I change MY CODE below to see what's inside -7d9d6f3d:15a658d8bb4:-7f27 (in terms of object property, restriction and range of restriction for the particular class at hand) ?
Thanks, Jos
MY CODE
ExtendedIterator classes = model.listClasses(); while
(classes.hasNext()) {
OntClass thisClass = (OntClass) classes.next();
ExtendedIterator properties = thisClass.listProperties();
while (properties.hasNext()){
Statement thisProperty = (Statement) properties.next();
if (thisProperty.getPredicate().toString().contains("sub")) {
System.out.println("Contains sub_P: " + thisProperty.getPredicate() + " Contains sub_O: " + thisProperty.getObject());
}
}
}
MY OUTPUT
[1] Contains sub_P: http://www.w3.org/2000/01/rdf-schema#subClassOf
http://www.bauhaus-luftfahrt.net/ontologies/2016/Ls_Ontology.owl#XXX
[2] Contains sub_P: http://www.w3.org/2000/01/rdf-schema#subClassOf
http://www.bauhaus-luftfahrt.net/ontologies/2016/Ls_Ontology.owl#YYY
[3] Contains sub_P: http://www.w3.org/2000/01/rdf-schema#subClassOf
Contains sub_O: -7d9d6f3d:15a658d8bb4:-7f27