/**
* 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 <code>owl:Thing</code> which is a super-class of
* both <code>u</code> and <code>v</code>. The algorithm is based on <a
* href="http://en.wikipedia.org/wiki/Tarjan's_off-line_least_common_ancestors_algorithm">Tarjan's
* off-line LCA</a>. The current implementation expects that the given model:
*
* <ul>
* <li>is transitively closed over the <code>subClassOf</code> relation
* <li>can cheaply determine <em>direct sub-class</em> relations
* </ul>
*
* <p>Both of these conditions are true of the built-in Jena OWL reasoners, such as {@link
* OntModelSpec#OWL_MEM_MICRO_RULE_INF}, and external DL reasoners such as Pellet.
*
* @param m The ontology model being queried to find the LCA, which should conform to the reasoner
* capabilities described above
* @param u An ontology class
* @param v An ontology class
* @return The LCA of <code>u</code> and <code>v</code>
* @exception JenaException if the language profile of the given model does not define a top
* concept (e.g. <code>owl:Thing</code>)
*/
public static OntClass getLCA(OntModel m, OntClass u, OntClass v) {
Resource root = m.getProfile().THING();
if (root == null) {
throw new JenaException(
"The given OntModel has a language profile that does not define a generic root class (such as owl:Thing)");
}
root = root.inModel(m);
return getLCA(m, root.as(OntClass.class), u, v);
}
/**
* Answer a list of the named hierarchy roots of a given {@link OntModel}. This will be similar to
* the results of {@link 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.
*
* @param m An ontology model
* @return A list of classes whose members are the named root classes of the class hierarchy in
* <code>m</code>
*/
public static List<OntClass> namedHierarchyRoots(OntModel m) {
List<OntClass> nhr = new ArrayList<OntClass>(); // named roots
List<OntClass> ahr = new ArrayList<OntClass>(); // anon roots
// do the initial partition of the root classes
partitionByNamed(m.listHierarchyRootClasses(), nhr, ahr);
// now push the fringe down until we have only named classes
while (!ahr.isEmpty()) {
OntClass c = ahr.remove(0);
partitionByNamed(c.listSubClasses(true), nhr, ahr);
}
return nhr;
}
