example04.java

本体推理工具 共八个例子:从如何建立本体到做一些简单的的本体推理

        // can be used to encode rules as well. To use it, we first initialize an instance
        // of the Namespaces class in the same way as in Example 2.
        Namespaces namespaces=new Namespaces();
        namespaces.registerPrefix("example04","http://kaon2.semanticweb.org/example04#");

        // We shall create a yet another rule that is similar to the above rule which says the following:
        //
        // If
        //     a person X knows about OWL
        // then
        //    the person X knowls about description logics as well.
        //
        // In Prolog, this rule would be written like this:
        //     personKnowsAboutTopic(X,example04:descriptionLogics) :- personKnowsAboutTopic(X,example04:owl)
        rule=(Rule)KAON2Manager.factory().axiom(
            "[rule ["+                                                                      // States that the rule follows. The opening brackes introduces a set of head literals.
            "    [[oprop example04:personKnowsAboutTopic] X [example04:descriptionLogics]]"+  // This is the specification of one head literal. The individuals must be enclosed in [].
            "  ] ["+                                                                        // The bracket ] terminated the set of head literals. The bracket [ opens the set of body literals.
            "    [[oprop example04:personKnowsAboutTopic] X [example04:owl]]"+                // This is the one body literal.
            "  ]"+                                                                          // This closes the set of body literals.
            "]"                                                                             // This closes the rule.
        ,namespaces);

        // We add the rule to the chande list.
        changes.add(new OntologyChangeEvent(rule,OntologyChangeEvent.ChangeType.ADD));

        // We now add some facts. We shall use these facts to query answering later.
        Individual boris=KAON2Manager.factory().individual("http://kaon2.semanticweb.org/example04#boris");
        // Boris is a student.
        changes.add(new OntologyChangeEvent(KAON2Manager.factory().classMember(student,boris),OntologyChangeEvent.ChangeType.ADD));
        // DIP is an EU project.
        Individual dip=KAON2Manager.factory().individual("http://kaon2.semanticweb.org/example04#dip");
        changes.add(new OntologyChangeEvent(KAON2Manager.factory().classMember(euProject,dip),OntologyChangeEvent.ChangeType.ADD));
        // DIP is about semantic web.
        changes.add(new OntologyChangeEvent(KAON2Manager.factory().objectPropertyMember(projectHasTopic,dip,semanticWeb),OntologyChangeEvent.ChangeType.ADD));
        // Boris works on DIP.
        changes.add(new OntologyChangeEvent(KAON2Manager.factory().objectPropertyMember(worksOn,boris,dip),OntologyChangeEvent.ChangeType.ADD));

        // We now apply the changes to the ontology. Only after this action is done,
        // the axioms created above are added to the ontology.
        ontology.applyChanges(changes);

        // We now save the ontology by calling the serializer. Observe that the
        // location where the ontology is stored does not need to be the same
        // as the physical URI. This is deliberate, as this allows you to implement
        // 'Save As' operation. The second parameter defines the character encoding used
        // in the XML file. we save the ontology into 'c:\temp\example04.xml'.
        System.out.println("The ontology will be saved into 'c:\\temp\\example04.xml'.");
        System.out.println("Please ensure that 'c:\\temp' directory exists.");
        ontology.saveOntology(OntologyFileFormat.OWL_XML,new File("c:\\temp\\example04.xml"),"ISO-8859-1");

        System.out.println("The ontology was saved successfully into 'c:\\temp\\example04.xml'.");

        // We are now ready to ask some questions. Our goal is to obtain the expertise of all persons. In order words,
        // we want to ask the following conjunctive query:
        //
        //   Person(X),personKnowsAboutTopic(X,Y)
        //
        // The first thing we need to do is create an instance of the reasoner. Reasoners consume resources, so you should keep
        // them around only for as long as you need them. However, if you plan to ask several queries, it is *MUCH* more efficient
        // to use one and the same reasoner for all queries. One reasoner can be used to run several concurrent queries. 
        Reasoner reasoner=ontology.createReasoner();

        // We now create the query object. A query consists of the following things:
        //
        // - a list of literals definint the query (they are created as usual)
        // - a list of distinguished variables, i.e. the variables that will be returned
        Query whatDoPeopleKnowAbout=reasoner.createQuery(new Literal[] {
            KAON2Manager.factory().literal(true,person,new Term[] { X }),
            KAON2Manager.factory().literal(true,personKnowsAboutTopic,new Term[] { X,Y }),
        },new Variable[] { X,Y});

        // Creating the query has the effect of compiling it. A single query can be executed then several times.
        // A query is executed by invoking the Query.open() method.
        System.out.println();
        System.out.println("The list of people and things that they know about:");
        System.out.println("---------------------------------------------------");

        whatDoPeopleKnowAbout.open();
        // We now iterate over the query results.
        while (!whatDoPeopleKnowAbout.afterLast()) {
            // A query result is a set of tuples. The values in each tuple correspond to the distinguished variables.
            // In the above example, the distinguished variables are [X,Y]; this means that the first object in
            // the tuple is the value for the X variable, and the second one is the value for the Y variable.
            Term[] tupleBuffer=whatDoPeopleKnowAbout.tupleBuffer();
            System.out.println("Person '"+tupleBuffer[0].toString()+"' knows about '"+tupleBuffer[1].toString()+"'.");
            whatDoPeopleKnowAbout.next();
        }

        System.out.println("---------------------------------------------------");

        // If a query has been successfully opened, it should also be closed; otherwise, a resource leak occurs.
        whatDoPeopleKnowAbout.close();
        
        // After a query is closed, it may be reopened. The results of the query will reflect the changes to the ontology.
        // To see this, we shall add an additional fact that DIP is about OWL.
        changes.clear();
        changes.add(new OntologyChangeEvent(KAON2Manager.factory().objectPropertyMember(projectHasTopic,dip,owl),OntologyChangeEvent.ChangeType.ADD));
        ontology.applyChanges(changes);

        System.out.println();
        System.out.println("New facts have been successfully added to the ontology.");
        System.out.println();

        // We now execute the query again. The results reflect the change in the ontology.
        System.out.println("The same query executed again:");
        System.out.println("---------------------------------------------------");

        whatDoPeopleKnowAbout.open();
        while (!whatDoPeopleKnowAbout.afterLast()) {
            Term[] tupleBuffer=whatDoPeopleKnowAbout.tupleBuffer();
            System.out.println("Person '"+tupleBuffer[0].toString()+"' knows about '"+tupleBuffer[1].toString()+"'.");
            whatDoPeopleKnowAbout.next();
        }
        System.out.println("---------------------------------------------------");
        whatDoPeopleKnowAbout.close();

        // When a query is not needed any more, it should be disposed of. Forgetting to do so will result in
        // a fairly serious memory leak.
        whatDoPeopleKnowAbout.dispose();
        
        // Reasoners have to be disposed off after they are not used any more. Forgetting to do so will result in
        // a fairly serious memory leak!
        reasoner.dispose();

        // Don't forget to close the connection!
        connection.close();
    }
}