Package org.apache.jena.ontology

Class OntTools

  • public class OntTools
extends java.lang.Object

    Some general utilities and algorithms to support developers working with the general classes in the Jena ontology API. Warning these utilities are experimental. Extensive testing has not yet occurred (see org.apache.jena.ontology.impl.TestOntTools in the test area for basic unit tests), and in particular performance testing has not been carried out yet. Users are advised to exercise caution before relying on these utilities in production code. Please send any comments or suggestions to the Jena support email list.

    • Nested Class Summary

      Nested Classes 
      Modifier and Type Class Description
      static class  OntTools.DisjointSet
      A simple representation of disjoint sets
      static class  OntTools.LCAIndex
      Simple data structure mapping RDF nodes to disjoint sets, and pairs of resources to their LCA.
      static class  OntTools.Path
      A path is an application of List containing only Statement objects, and in which for all adjacent elements Si-1 and Si, where i > 0, it is true that:
      static class  OntTools.PredicatesFilter
      A filter which accepts statements whose predicate matches one of a collection of predicates held by the filter object.

    • Constructor Summary

      Constructors 
      Constructor Description
      OntTools()  

    • Constructor Detail

      • OntTools

        public OntTools()

    • Method Detail

      • getLCA

        public static OntClass getLCA​(OntModel m,
                              OntClass u,
                              OntClass v)

        Answer the lowest common ancestor of two classes in a given ontology. This is the class that is farthest from the root concept (defaulting to owl:Thing which is a super-class of both u and v. The algorithm is based on Tarjan's off-line LCA. The current implementation expects that the given model:

        • is transitively closed over the subClassOf relation
        • can cheaply determine direct sub-class relations

        Both of these conditions are true of the built-in Jena OWL reasoners, such as OntModelSpec.OWL_MEM_MICRO_RULE_INF, and external DL reasoners such as Pellet.

        Parameters:
        m - The ontology model being queried to find the LCA, which should conform to the reasoner capabilities described above
        u - An ontology class
        v - An ontology class
        Returns:
        The LCA of u and v
        Throws:
        JenaException - if the language profile of the given model does not define a top concept (e.g. owl:Thing)

      • getLCA

        public static OntClass getLCA​(OntModel m,
                              OntClass root,
                              OntClass u,
                              OntClass v)
        Answer the lowest common ancestor of two classes, assuming that the given class is the root concept to start searching from. See getLCA(OntModel, OntClass, OntClass) for details.
        Parameters:
        m - The ontology model being queried to find the LCA, which should conform to the reasoner capabilities described above
        root - The root concept, which will be the starting point for the algorithm
        u - An ontology class
        v - An ontology class
        Returns:
        The LCA of u and v
        Throws:
        JenaException - if the language profile of the given model does not define a top concept (e.g. owl:Thing)

      • findShortestPath

        public static OntTools.Path findShortestPath​(Model m,
                                             Resource start,
                                             RDFNode end,
                                             java.util.function.Predicate<Statement> onPath)

        Answer the shortest path from the start resource to the end RDF node, such that every step on the path is accepted by the given filter. A path is a List of RDF Statements. The subject of the first statement in the list is start, and the object of the last statement in the list is end.

        The onPath argument is a Predicate, which accepts a statement and returns true if the statement should be considered to be on the path. To search for an unconstrained path, pass ()->true as an argument. To search for a path whose predicates match a fixed restricted set of property names, pass an instance of OntTools.PredicatesFilter.

        If there is more than one path of minimal length from start to end, this method returns an arbitrary one. The algorithm is blind breadth-first search, with loop detection.

        Parameters:
        m - The model in which we are seeking a path
        start - The starting resource
        end - The end, or goal, node
        onPath - A filter which determines whether a given statement can be considered part of the path
        Returns:
        A path, consisting of a list of statements whose first subject is start, and whose last object is end, or null if no such path exists.

      • namedHierarchyRoots

        public static java.util.List<OntClass> namedHierarchyRoots​(OntModel m)
        Answer a list of the named hierarchy roots of a given OntModel. This will be similar to the results of OntModel.listHierarchyRootClasses(), with the added constraint that every member of the returned iterator will be a named class, not an anonymous class expression. The named root classes are calculated from the root classes, by recursively replacing every anonymous class with its direct sub-classes. Thus it can be seen that the values in the list consists of the shallowest fringe of named classes in the hierarchy.
        Parameters:
        m - An ontology model
        Returns:
        A list of classes whose members are the named root classes of the class hierarchy in m