com.hp.hpl.jena.ontology

Class OntTools

java.lang.Object

com.hp.hpl.jena.ontology.OntTools

public class OntTools
extends 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 com.hp.hpl.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 and 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 and Description
OntTools()

Method Summary

Methods

Modifier and Type	Method and Description
static OntTools.Path	findShortestPath(Model m, Resource start, RDFNode end, com.hp.hpl.jena.util.iterator.Filter<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.
static OntClass	getLCA(OntModel m, OntClass u, OntClass v) Answer the lowest common ancestor of two classes in a given ontology.
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.
static List<OntClass>	namedHierarchyRoots(OntModel m) Answer a list of the named hierarchy roots of a given OntModel.

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

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,
                             com.hp.hpl.jena.util.iterator.Filter<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 Filter, 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 Filter.any 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 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