CODEWITHSUNDEEP
jenauser-defined-data-types
akos
akos

Reputation: 13

How to create user defined datatypes in Apache Jena?

I'm creating an ontology using Apache Jena. However, I can't find a way of creating custom datatypes as in the following example: 'has value' some xsd:float[>= 0.0f , <= 15.0f].

Do you have any ideas?

Upvotes: 1

Views: 663

Answers (1)

ssz
ssz

Reputation: 835

It seems what you need is DatatypeRestriction with two facet restrictions: xsd:minInclusive and xsd:maxInclusive. It is OWL2 constructions.

org.apache.jena.ontology.OntModel does not support OWL2, only OWL1.1 partially (see documentation), and, therefore, there are no builtin methods for creating such data-ranges (there is only DataOneOf data range expression, see OntModel#createDataRange(RDFList)).

So you have to create a desired datatype manually, triple by triple, using the general org.apache.jena.rdf.model.Model interface. In RDF, it would look like this:

_:x rdf:type rdfs:Datatype.
_:x owl:onDatatype DN.
_:x owl:withRestrictions (_:x1 ... _:xn).

See also owl2-quick-guide.

Or, to build such an ontology, you can use some external utilities or APIs. For example, in ONT-API (v. 2.x.x) the following snippet

    String ns = "https://stackoverflow.com/questions/54131709#";
    OntModel m = OntModelFactory.createModel()
            .setNsPrefixes(OntModelFactory.STANDARD).setNsPrefix("q", ns);
    OntDataRange.Named floatDT = m.getDatatype(XSD.xfloat);
    OntFacetRestriction min = m.createFacetRestriction(OntFacetRestriction.MinInclusive.class,
            floatDT.createLiteral("0.0"));
    OntFacetRestriction max = m.createFacetRestriction(OntFacetRestriction.MaxInclusive.class,
            floatDT.createLiteral("15.0"));
    OntDataRange.Named myDT = m.createDatatype(ns + "MyDatatype");
    myDT.addEquivalentClass(m.createDataRestriction(floatDT, min, max));
    m.createResource().addProperty(m.createDataProperty(ns + "someProperty"),
            myDT.createLiteral("2.2"));
    m.write(System.out, "ttl");

will produce the following ontology:

@prefix q:     <https://stackoverflow.com/questions/54131709#> .
@prefix rdf:   <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
@prefix owl:   <http://www.w3.org/2002/07/owl#> .
@prefix xsd:   <http://www.w3.org/2001/XMLSchema#> .
@prefix rdfs:  <http://www.w3.org/2000/01/rdf-schema#> .

[ q:someProperty  "2.2"^^q:MyDatatype ] .

q:MyDatatype  a              rdfs:Datatype ;
        owl:equivalentClass  [ a                     rdfs:Datatype ;
                               owl:onDatatype        xsd:float ;
                               owl:withRestrictions  ( [ xsd:minInclusive  "0.0"^^xsd:float ]
                                                       [ xsd:maxInclusive  "15.0"^^xsd:float ]
                                                     )
                             ] .

q:someProperty  a  owl:DatatypeProperty .

Upvotes: 1

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