1 files changed, 258 insertions, 0 deletions

diff --git a/src/uk/ac/ox/cs/pagoda/hermit/TermGraph.java b/src/uk/ac/ox/cs/pagoda/hermit/TermGraph.java
new file mode 100644
index 0000000..0041cca
--- /dev/null
+++ b/src/uk/ac/ox/cs/pagoda/hermit/TermGraph.java
@@ -0,0 +1,258 @@
+package uk.ac.ox.cs.pagoda.hermit;
+
+import java.util.Collection;
+import java.util.Comparator;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.Iterator;
+import java.util.Map;
+import java.util.PriorityQueue;
+import java.util.Set;
+
+import org.semanticweb.HermiT.model.AnnotatedEquality;
+import org.semanticweb.HermiT.model.Atom;
+import org.semanticweb.HermiT.model.AtomicConcept;
+import org.semanticweb.HermiT.model.AtomicRole;
+import org.semanticweb.HermiT.model.Constant;
+import org.semanticweb.HermiT.model.DLClause;
+import org.semanticweb.HermiT.model.DLPredicate;
+import org.semanticweb.HermiT.model.DatatypeRestriction;
+import org.semanticweb.HermiT.model.Equality;
+import org.semanticweb.HermiT.model.Individual;
+import org.semanticweb.HermiT.model.NodeIDLessEqualThan;
+import org.semanticweb.HermiT.model.NodeIDsAscendingOrEqual;
+import org.semanticweb.HermiT.model.Term;
+import org.semanticweb.HermiT.model.Variable;
+
+import uk.ac.ox.cs.pagoda.util.Namespace;
+import uk.ac.ox.cs.pagoda.util.Utility;
+
+public class TermGraph {
+        
+        Map<Term, Collection<Edge>> graph = new HashMap<Term, Collection<Edge>>(); 
+        Map<Term, Collection<AtomicConcept>> term2concepts = new HashMap<Term, Collection<AtomicConcept>>();
+        Set<Term> choosen = new HashSet<Term>(), allTerms = new HashSet<Term>(); 
+        DLClause clause;
+        Set<Atom> newBodyAtoms = new HashSet<Atom>(); 
+
+        public TermGraph(DLClause clause) {
+                this.clause = clause; 
+                for (Atom atom: clause.getHeadAtoms())
+                        for (int i = 0; i < atom.getArity(); ++i)
+                                allTerms.add(atom.getArgument(i)); 
+                for (Atom atom: clause.getBodyAtoms())
+                        for (int i = 0; i < atom.getArity(); ++i)
+                                allTerms.add(atom.getArgument(i)); 
+        }
+        
+        public DLClause simplify() {
+                constructGraph(); 
+                chooseTerms(); 
+                
+                PriorityQueue<Term> queue = new PriorityQueue<Term>(allTerms.size(), new Comparator<Term>() {
+
+                        @Override
+                        public int compare(Term o1, Term o2) {
+                                int diff = 0; 
+                                @SuppressWarnings("rawtypes")
+                                Collection set1 = term2concepts.get(o1), set2 = term2concepts.get(o2);
+                                int num1 = size(set1), num2 = size(set2); 
+                                
+                                if ((diff = num2 - num1) != 0) 
+                                        return diff;
+                                
+                                set1 = graph.get(o1); set2 = graph.get(o2); 
+                                num1 = size(set1); num2 = size(set2); 
+                                
+                                return num2 - num1; 
+                        }
+                        
+                        private int size(@SuppressWarnings("rawtypes") Collection c) {
+                                return c == null ? 0 : c.size();
+                        }
+                        
+                });
+                
+                for (Term term: allTerms)
+                        queue.add(term);
+                
+                while (!queue.isEmpty()) {
+                        Term term = queue.remove();
+                        if (!choosen.contains(term) && isRepresentative(term)) 
+                                choosen.add(term);
+                }
+
+                boolean flag; 
+                for (Iterator<Atom> iter = newBodyAtoms.iterator(); iter.hasNext(); ) {
+                        flag = true; 
+                        Atom atom = iter.next(); 
+                        for (int i = 0; i < atom.getArity(); ++i) {
+                                if (!choosen.contains(atom.getArgument(i))) {
+                                        flag = false; 
+                                        break; 
+                                }
+                        }
+                        if (!flag) iter.remove(); 
+                }
+                
+                return DLClause.create(clause.getHeadAtoms(), newBodyAtoms.toArray(new Atom[0])); 
+        }
+        
+        private boolean isRepresentative(Term term) {
+                boolean flag = true; 
+                for (Term otherTerm: choosen) 
+                        if (!term.equals(otherTerm) && isSubsumedBy(term, otherTerm)) {
+                                flag = false; 
+                        }
+                return flag;
+        }
+        
+        private boolean isSubsumedBy(Term t1, Term t2) {
+                Collection<AtomicConcept> set1 = term2concepts.get(t1);
+                Collection<AtomicConcept> set2 = term2concepts.get(t2);
+                
+                if (set1 != null)
+                        if (set2 == null)
+                                return false;
+                        else if (!set2.containsAll(set1))
+                                return false; 
+                
+                Collection<Edge> edgeSet1 = graph.get(t1);  
+                Collection<Edge> edgeSet2 = graph.get(t2);
+                if (edgeSet1 != null)
+                        if (edgeSet2 == null)
+                                return false; 
+                        else {
+                                if (!edgeSet2.containsAll(edgeSet1))
+                                        return false;
+//                              else {
+//                                      Collection<Edge> restEdge1 = new HashSet<Edge>(); 
+//                                      for (Edge edge: edgeSet1)
+//                                              if (edge.term == t2); 
+//                                              else restEdge1.add(edge);
+//                                      
+//                                      Collection<Edge> restEdge2 = new HashSet<Edge>(); 
+//                                      for (Edge edge: edgeSet2)
+//                                              if (edge.term == t1); 
+//                                              else restEdge2.add(edge);
+//                                      
+//                                      return restEdge2.containsAll(edgeSet1);
+//                              }
+                        }
+                
+                return true; 
+        }
+
+        private void chooseTerms() {
+                Set<Variable> headVariables = new HashSet<Variable>(); 
+                for (Atom atom: clause.getHeadAtoms()) {
+                        atom.getVariables(headVariables);
+                }
+                choosen.addAll(headVariables); 
+                
+                for (Term term: allTerms) 
+                        if (term instanceof Constant || term instanceof Individual)
+                                choosen.add(term);
+
+                if (choosen.isEmpty()) choosen.add(Variable.create("X")); 
+//              propagate();
+        }
+
+//      private void propagate() {
+//              LinkedList<Term> queue = new LinkedList<Term>(choosen);
+//              Term term; 
+//              while (!queue.isEmpty()) {
+//                      term = queue.pop(); 
+//                      if (graph.containsKey(term))
+//                              for (Edge edge: graph.get(term)) 
+//                                      if (!choosen.contains(edge.term)) {
+//                                              choosen.add(edge.term); 
+//                                              queue.add(term); 
+//                                      }
+//              }
+//      }
+
+        private void constructGraph() {
+                DLPredicate p; 
+                for (Atom bodyAtom: clause.getBodyAtoms()) {
+                        p = bodyAtom.getDLPredicate(); 
+                        if (p instanceof AtomicConcept) {
+                                newBodyAtoms.add(bodyAtom); 
+                                addConcept(bodyAtom.getArgument(0), (AtomicConcept) p);
+                        }
+                        else if (p instanceof AtomicRole) {
+                                newBodyAtoms.add(bodyAtom); 
+                                addEdges(bodyAtom.getArgument(0), bodyAtom.getArgument(1), (AtomicRole) p);
+                        }
+                        else if (p instanceof DatatypeRestriction) 
+                                newBodyAtoms.add(bodyAtom); 
+                        else if (p instanceof NodeIDLessEqualThan || p instanceof NodeIDsAscendingOrEqual);  
+                        else if (p instanceof Equality || p instanceof AnnotatedEquality) {
+                                newBodyAtoms.add(bodyAtom); 
+                                addEdges(bodyAtom.getArgument(0), bodyAtom.getArgument(1), AtomicRole.create(Namespace.EQUALITY)); 
+                        } else {
+                                Utility.logError("Unknown DLPredicate in TermGraph: " + p);
+                        }
+                }
+        }
+        
+        private void addEdges(Term t1, Term t2, AtomicRole p) {
+                addEdge(t1, new Edge(p, t2, false));
+                addEdge(t2, new Edge(p, t1, true)); 
+        }
+
+        private void addEdge(Term t, Edge edge) {
+                Collection<Edge> edges; 
+                if ((edges = graph.get(t)) == null) {
+                        graph.put(t, edges = new HashSet<Edge>()); 
+                }
+                edges.add(edge);                
+        }
+
+        private void addConcept(Term t, AtomicConcept p) {
+                Collection<AtomicConcept> concepts; 
+                if ((concepts = term2concepts.get(t)) == null) {
+                        term2concepts.put(t, concepts = new HashSet<AtomicConcept>()); 
+                }
+                concepts.add(p);                
+        }
+
+        public boolean mark(Term t) {
+                return choosen.add(t);  
+        }
+        
+}
+
+class Edge {
+        boolean isInverse; 
+        AtomicRole role; 
+        Term term; 
+        
+        public Edge(AtomicRole role, Term term, boolean isInverse) {
+                this.role = role; 
+                this.term = term; 
+                this.isInverse = isInverse; 
+        }
+        
+        @Override
+        public int hashCode() {
+                return role.hashCode() * 1997 + term.hashCode() * 2 + (isInverse ? 1 : 0); 
+        }
+        
+        @Override
+        public boolean equals(Object obj) {
+                if (!(obj instanceof Edge)) return false; 
+                Edge other = (Edge) obj; 
+                return isInverse == other.isInverse && role.equals(other.role) && term.equals(other.term);  
+        }
+        
+        @Override
+        public String toString() {
+                if (isInverse)
+                        return "inv_" + role.toString() + "_" + term.toString();
+                return role.toString() + "_" + term.toString();
+        }
+        
+}
+
+