1 files changed, 5 insertions, 2 deletions

diff --git a/src/uk/ac/ox/cs/pagoda/tracking/TrackingRuleEncoderWithGap.java b/src/uk/ac/ox/cs/pagoda/tracking/TrackingRuleEncoderWithGap.java
index e7bd188..67d07a8 100644
--- a/src/uk/ac/ox/cs/pagoda/tracking/TrackingRuleEncoderWithGap.java
+++ b/src/uk/ac/ox/cs/pagoda/tracking/TrackingRuleEncoderWithGap.java
@@ -3,10 +3,12 @@ package uk.ac.ox.cs.pagoda.tracking;
 import java.util.Collection;
 import java.util.LinkedList;
 
+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.DLClause;
+import org.semanticweb.HermiT.model.Equality;
 import org.semanticweb.HermiT.model.Variable;
 import org.semanticweb.owlapi.model.OWLClass;
 import org.semanticweb.owlapi.model.OWLObjectProperty;
@@ -83,11 +85,12 @@ public class TrackingRuleEncoderWithGap extends TrackingRuleEncoder {
                 }
 
                 DLClause newClause;
+                headAtom = clause.getHeadAtom(0);
                 
-                int offset = (clause.getBodyLength() == 1 && clause.getBodyAtom(0).getDLPredicate().toString().contains("owl:Nothing")) ? 1 : 2; 
+                boolean equalityHead = headAtom.getDLPredicate() instanceof Equality || headAtom.getDLPredicate() instanceof AnnotatedEquality; 
+                int offset = (equalityHead || (clause.getBodyLength() == 1 && clause.getBodyAtom(0).getDLPredicate().toString().contains("owl:Nothing"))) ? 1 : 2;
                 
                 Atom[] newBodyAtoms = new Atom[clause.getBodyLength() + offset];
-                headAtom = clause.getHeadAtom(0);
                 newBodyAtoms[0] = Atom.create(
                                 getTrackingDLPredicate(headAtom.getDLPredicate()), 
                                 DLClauseHelper.getArguments(headAtom));