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package uk.ac.ox.cs.pagoda.constraints;
import java.util.Collection;
import java.util.HashSet;
import java.util.LinkedList;
import java.util.Set;
import org.semanticweb.HermiT.model.Atom;
import org.semanticweb.HermiT.model.AtomicConcept;
import org.semanticweb.HermiT.model.DLClause;
import org.semanticweb.HermiT.model.Individual;
import org.semanticweb.HermiT.model.Term;
import org.semanticweb.HermiT.model.Variable;
public class UnaryBottom implements BottomStrategy {
@Override
public Collection<DLClause> process(Collection<DLClause> clauses) {
Collection<DLClause> ret = new LinkedList<DLClause>();
for (DLClause clause: clauses)
if (clause.getHeadLength() == 0) {
ret.add(DLClause.create(getEmptyHead(pickRepresentative(clause.getBodyAtoms())), clause.getBodyAtoms()));
}
else
ret.add(clause);
return ret;
}
protected Term pickRepresentative(Atom[] atoms) {
Term rep = null;
Set<Variable> vars = new HashSet<Variable>();
for (Atom atom: atoms) {
atom.getVariables(vars);
for (Variable v: vars)
if (rep == null || ((Variable) rep).getName().compareTo(v.getName()) > 0)
rep = v;
vars.clear();
}
if (rep != null) return rep;
Set<Individual> inds = new HashSet<Individual>();
for (Atom atom: atoms) {
atom.getIndividuals(inds);
for (Individual i: inds)
if (rep == null || ((Individual) rep).getIRI().compareTo(i.getIRI()) > 0)
rep = i;
inds.clear();
}
return rep;
}
@Override
public boolean isBottomRule(DLClause clause) {
return clause.getHeadLength() == 1 && clause.getHeadAtom(0).getDLPredicate().equals(AtomicConcept.NOTHING);
}
public Atom[] getEmptyHead(Term t) {
return new Atom[] {Atom.create(AtomicConcept.NOTHING, t)};
}
@Override
public int getBottomNumber() {
return 1;
}
}
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