How to make implicit properties explicit

[Stefan]

Hi,

I'm trying to plot my ontology as a graph. For this I need to add explicit property relations for inverse properties.

E.g. I have the following object properties: A, B; A is the inverse of B
And the individuals: Ind1, Ind2

The ontology contains the following information: Ind1 A Ind2

Implicitly, it also contains Ind2 B Ind1. How do I make this explicit?
I tried using the reasoners, which works in Protege, but didn't help in OR2. I also have tried using the new infer_property_values (Even though I don't quite understand what it's supposed to do), but that just gave me an error message.

I also tried exporting my inferred relations from protege somehow, which would be an acceptable workaround, but didn't manage to do that, either.

[Jiba]

Hi,

In ontologies, it is usually common to not store explicitely invert property values (to save space).

What kind of error do you get with infer_property_values ? I think it is the right approach (although I might prevented saving the invert property values for saving space, I need to check that).

Best regards,
Jiba

[Stefan]

Hi,

Thank you for your quick response.

> In ontologies, it is usually common to not store explicitely invert property values (to save space).

As an alternative, a way to query implicit property relations would work, too. I've been using get_properties(), and going with the example above, it would only return A when querying from Ind1, but not B when querying from Ind2.

When trying to use infer_property_values, I get the following error:

Traceback (most recent call last):
  File "<PATH>/main.py", line 106, in <module>
    or2.sync_reasoner(infer_property_values=True)
  File "<PATH>/venv/lib/python3.5/site-packages/owlready2/reasoning.py", line 177, in sync_reasoner_hermit
    a, b = pair[1:-1].split(">, <", 1)
ValueError: not enough values to unpack (expected 2, got 1)

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "<PATH>/main.py", line 106, in <module>
    or2.sync_reasoner(infer_property_values=True)
  File "<PATH>/venv/lib/python3.5/site-packages/owlready2/namespace.py", line 666, in __exit__
    Namespace.__exit__(self, exc_type, exc_val, exc_tb)
  File "<PATH>/venv/lib/python3.5/site-packages/owlready2/namespace.py", line 68, in __exit__
    if self.world.graph: self.world.graph.release_write_lock()
  File "<PATH>/venv/lib/python3.5/site-packages/owlready2/triplelite.py", line 373, in release_write_lock
    self.lock.release()
RuntimeError: cannot release un-acquired lock

[Jiba]

Hi,

get_properties() does not return inverse properties, but that was never intended -- it is more a bug or a missing feature.
I fixed it in the development version on Bitbucket : get_properties() now considers inverse properties.

Regarding the reasoning error, could you send me some ontology that I can use to reproduce the problem ?

Best regards,
Jiba

[Stefan]

Hi,

thanks a lot for the quick fix.

I was able to reproduce the error using the following setup:

Python script:
import owlready2 as or2

o = or2.get_ontology("file://<PATH>.owl").load()

with o:
    or2.sync_reasoner(infer_property_values=True)


OWL file:
<?xml version="1.0"?>
<rdf:RDF xmlns="http://www.semanticweb.org/stlu/ontologies/2019/1/untitled-ontology-117#"
     xml:base="http://www.semanticweb.org/stlu/ontologies/2019/1/untitled-ontology-117"
     xmlns:owl="http://www.w3.org/2002/07/owl#"
     xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
     xmlns:xml="http://www.w3.org/XML/1998/namespace"
     xmlns:xsd="http://www.w3.org/2001/XMLSchema#"
     xmlns:rdfs="http://www.w3.org/2000/01/rdf-schema#">
    <owl:Ontology rdf:about="http://www.semanticweb.org/stlu/ontologies/2019/1/untitled-ontology-117"/>
   


   

   


   

    <owl:ObjectProperty rdf:about="http://www.semanticweb.org/stlu/ontologies/2019/1/untitled-ontology-117#Prop1"/>
   


   

    <owl:ObjectProperty rdf:about="http://www.semanticweb.org/stlu/ontologies/2019/1/untitled-ontology-117#Prop2"/>
   


   

   


   

    <owl:Class rdf:about="http://www.semanticweb.org/stlu/ontologies/2019/1/untitled-ontology-117#A"/>
   


   

    <owl:Class rdf:about="http://www.semanticweb.org/stlu/ontologies/2019/1/untitled-ontology-117#B"/>
   


   

    <owl:Class rdf:about="http://www.semanticweb.org/stlu/ontologies/2019/1/untitled-ontology-117#C"/>
   


   

   


   

    <owl:NamedIndividual rdf:about="http://www.semanticweb.org/stlu/ontologies/2019/1/untitled-ontology-117#a"/>
   


   

    <owl:NamedIndividual rdf:about="http://www.semanticweb.org/stlu/ontologies/2019/1/untitled-ontology-117#b"/>
   


   

    <owl:NamedIndividual rdf:about="http://www.semanticweb.org/stlu/ontologies/2019/1/untitled-ontology-117#c"/>
   


   

    <rdf:Description>
        <rdf:type rdf:resource="http://www.w3.org/2002/07/owl#AllDisjointClasses"/>
        <owl:members rdf:parseType="Collection">
            <rdf:Description rdf:about="http://www.semanticweb.org/stlu/ontologies/2019/1/untitled-ontology-117#A"/>
            <rdf:Description rdf:about="http://www.semanticweb.org/stlu/ontologies/2019/1/untitled-ontology-117#B"/>
            <rdf:Description rdf:about="http://www.semanticweb.org/stlu/ontologies/2019/1/untitled-ontology-117#C"/>
        </owl:members>
    </rdf:Description>
</rdf:RDF>

[Jiba]

Hi,

There was a bug in the parsing of the HermiT results. I fixed it in the development version. (NB Pellet was not affected by this bug).

Thank you for reporting this problem.

Best regards,
Jiba