Determining class/individual relationships based on values computed at runtime

Question

I have a simple ontology that consists of a Weather class and some subclasses (although I'm not sure if I should make them individuals instead) such as "Cold", "Rainy", "Sunny", etc. The thing is, I don't know which of these conditions hold until I get weather data at runtime. For instance, it is only "Cold" if the current temperature is less than, say, 70 degrees (I live in Texas ;p). Is there a way to structure the ontology so that this sort of reasoning can be done at runtime? (I am using Protege and Jena.)

Basically, I want to do different things based on which weather conditions are currently valid. For simplicity's sake, let's assume I just want to print out "It is currently cold, rainy ...", listing out the current weather conditions based on data such as temperature and amount of precipitation.

Answer 1

Writing the axioms in OWL

It sounds like you're trying to add some rules of the form:

If x has a temperature less than or equal to 32.0 F, then x has weather condition Cold.
If x has a temperature above 32.0 F and less than or equal to 70.0 F, then x has weather condition Warm.
If x has a temperature above 70.0 F, then x has weather condition Hot.

You can do these in OWL without much problem with axioms like

hasTemperature some double[> 32.0, <= 70.0] SubClassOf hasWeatherCondition value Warm

These are called general class axioms because they have class expressions rather than atomic class names on the left hand side. The full set that I described above would be entered in Protégé as follows:

Seeing the results with Jena and Pellet

To do the reasoning about numbers, you'll need a reasoner. I'm not sure whether or not Jena's rule reasoners can do this type of reasoning or not, but I know that Pellet can. The following code uses a Pellet-backed inference model.

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;

import org.mindswap.pellet.jena.PelletReasonerFactory;

import com.hp.hpl.jena.datatypes.xsd.XSDDatatype;
import com.hp.hpl.jena.ontology.Individual;
import com.hp.hpl.jena.ontology.OntModel;
import com.hp.hpl.jena.ontology.OntProperty;
import com.hp.hpl.jena.rdf.model.ModelFactory;
import com.hp.hpl.jena.rdf.model.RDFNode;
import com.hp.hpl.jena.rdf.model.StmtIterator;
import com.hp.hpl.jena.vocabulary.OWL;

public class WeatherExample {
    public static void main(String[] args) throws FileNotFoundException, IOException {
        final String NS = "http://stackoverflow.com/q/20489574/1281433/weather#";

        // Create an OntModel and read in the content from the ontology.  We're creating an model
        // that has Pellet doing inference behind the scenes. Pellet can handle the types of datatype
        // reasoning that we need for this particular problem.
        final OntModel model = ModelFactory.createOntologyModel( PelletReasonerFactory.THE_SPEC );
        try ( final FileInputStream in = new FileInputStream( "/home/taylorj/tmp/ontologies/weather/weather.owl" )) {
            model.read( in, null, "RDF/XML" );
        }

        // create an individual and list the things that the model knows about it.
        final Individual todaysWeather = model.createIndividual( NS+"weatherOfToday", OWL.Thing );
        System.out.println( "== Initial Knowledge ==" );
        for ( final StmtIterator it = model.listStatements( todaysWeather, null, (RDFNode) null ); it.hasNext(); ) {
            System.out.println( it.next() );
        }

        // Add the information that todaysWeather had temperature 28.0.
        final OntProperty hasTemperature = model.createOntProperty( NS+"hasTemperature" );
        todaysWeather.addLiteral( hasTemperature, model.createTypedLiteral( "28.0", XSDDatatype.XSDdouble ));

        // Show the new knowledge about todaysWeather.
        System.out.println( "== Later Knowledge ==" );
        for ( final StmtIterator it = model.listStatements( todaysWeather, null, (RDFNode) null ); it.hasNext(); ) {
            System.out.println( it.next() );
        }
    }
}

The output follows. Notice that in the second chunk todaysWeather hasWeatherCondition Cold.

== Initial Knowledge ==
[http://stackoverflow.com/q/20489574/1281433/weather#weatherOfToday, http://www.w3.org/1999/02/22-rdf-syntax-ns#type, http://www.w3.org/2002/07/owl#Thing]
[http://stackoverflow.com/q/20489574/1281433/weather#weatherOfToday, http://www.w3.org/2002/07/owl#sameAs, http://stackoverflow.com/q/20489574/1281433/weather#weatherOfToday]

== Later Knowledge ==
[http://stackoverflow.com/q/20489574/1281433/weather#weatherOfToday, http://www.w3.org/1999/02/22-rdf-syntax-ns#type, http://www.w3.org/2002/07/owl#Thing]
[http://stackoverflow.com/q/20489574/1281433/weather#weatherOfToday, http://www.w3.org/2002/07/owl#sameAs, http://stackoverflow.com/q/20489574/1281433/weather#weatherOfToday]
[http://stackoverflow.com/q/20489574/1281433/weather#weatherOfToday, http://stackoverflow.com/q/20489574/1281433/weather#hasWeatherCondition, http://stackoverflow.com/q/20489574/1281433/weather#Cold]
[http://stackoverflow.com/q/20489574/1281433/weather#weatherOfToday, http://stackoverflow.com/q/20489574/1281433/weather#hasTemperature, "28.0"^^http://www.w3.org/2001/XMLSchema#double]

The ontology

You can copy and paste the content of the ontology from which I made the screenshot from the following.

<rdf:RDF
    xmlns="http://stackoverflow.com/q/20489574/1281433/weather#"
    xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
    xmlns:owl="http://www.w3.org/2002/07/owl#"
    xmlns:xsd="http://www.w3.org/2001/XMLSchema#"
    xmlns:rdfs="http://www.w3.org/2000/01/rdf-schema#">
  <owl:Ontology rdf:about="http://stackoverflow.com/q/20489574/1281433/weather"/>
  <owl:ObjectProperty rdf:about="http://stackoverflow.com/q/20489574/1281433/weather#hasWeatherCondition"/>
  <owl:DatatypeProperty rdf:about="http://stackoverflow.com/q/20489574/1281433/weather#hasTemperature">
    <rdfs:comment>temperature in degrees Fahrenheit </rdfs:comment>
    <rdfs:range rdf:resource="http://www.w3.org/2001/XMLSchema#double"/>
  </owl:DatatypeProperty>
  <owl:Restriction>
    <rdfs:subClassOf>
      <owl:Restriction>
        <owl:onProperty rdf:resource="http://stackoverflow.com/q/20489574/1281433/weather#hasWeatherCondition"/>
        <owl:hasValue>
          <owl:NamedIndividual rdf:about="http://stackoverflow.com/q/20489574/1281433/weather#Hot"/>
        </owl:hasValue>
      </owl:Restriction>
    </rdfs:subClassOf>
    <owl:onProperty rdf:resource="http://stackoverflow.com/q/20489574/1281433/weather#hasTemperature"/>
    <owl:someValuesFrom>
      <rdfs:Datatype>
        <owl:onDatatype rdf:resource="http://www.w3.org/2001/XMLSchema#double"/>
        <owl:withRestrictions rdf:parseType="Collection">
          <rdf:Description>
            <xsd:minExclusive rdf:datatype="http://www.w3.org/2001/XMLSchema#double"
            >70.0</xsd:minExclusive>
          </rdf:Description>
        </owl:withRestrictions>
      </rdfs:Datatype>
    </owl:someValuesFrom>
  </owl:Restriction>
  <owl:Restriction>
    <rdfs:subClassOf>
      <owl:Restriction>
        <owl:onProperty rdf:resource="http://stackoverflow.com/q/20489574/1281433/weather#hasWeatherCondition"/>
        <owl:hasValue>
          <owl:NamedIndividual rdf:about="http://stackoverflow.com/q/20489574/1281433/weather#Warm"/>
        </owl:hasValue>
      </owl:Restriction>
    </rdfs:subClassOf>
    <owl:onProperty rdf:resource="http://stackoverflow.com/q/20489574/1281433/weather#hasTemperature"/>
    <owl:someValuesFrom>
      <rdfs:Datatype>
        <owl:onDatatype rdf:resource="http://www.w3.org/2001/XMLSchema#double"/>
        <owl:withRestrictions rdf:parseType="Collection">
          <rdf:Description>
            <xsd:maxInclusive rdf:datatype="http://www.w3.org/2001/XMLSchema#double"
            >70.0</xsd:maxInclusive>
          </rdf:Description>
          <rdf:Description>
            <xsd:minExclusive rdf:datatype="http://www.w3.org/2001/XMLSchema#double"
            >32.0</xsd:minExclusive>
          </rdf:Description>
        </owl:withRestrictions>
      </rdfs:Datatype>
    </owl:someValuesFrom>
  </owl:Restriction>
  <owl:Restriction>
    <rdfs:subClassOf>
      <owl:Restriction>
        <owl:onProperty rdf:resource="http://stackoverflow.com/q/20489574/1281433/weather#hasWeatherCondition"/>
        <owl:hasValue>
          <owl:NamedIndividual rdf:about="http://stackoverflow.com/q/20489574/1281433/weather#Cold"/>
        </owl:hasValue>
      </owl:Restriction>
    </rdfs:subClassOf>
    <owl:onProperty rdf:resource="http://stackoverflow.com/q/20489574/1281433/weather#hasTemperature"/>
    <owl:someValuesFrom>
      <rdfs:Datatype>
        <owl:onDatatype rdf:resource="http://www.w3.org/2001/XMLSchema#double"/>
        <owl:withRestrictions rdf:parseType="Collection">
          <rdf:Description>
            <xsd:maxInclusive rdf:datatype="http://www.w3.org/2001/XMLSchema#double"
            >32.0</xsd:maxInclusive>
          </rdf:Description>
        </owl:withRestrictions>
      </rdfs:Datatype>
    </owl:someValuesFrom>
  </owl:Restriction>
</rdf:RDF>