diff --git a/org.ntlab.traceCollector/src/org/ntlab/traceCollector/tracer/trace/Alias.java b/org.ntlab.traceCollector/src/org/ntlab/traceCollector/tracer/trace/Alias.java
index f7a436a..e2ce931 100644
--- a/org.ntlab.traceCollector/src/org/ntlab/traceCollector/tracer/trace/Alias.java
+++ b/org.ntlab.traceCollector/src/org/ntlab/traceCollector/tracer/trace/Alias.java
@@ -54,6 +54,11 @@
 	public MethodExecution getMethodExecution() {
 		return occurrencePoint.getMethodExecution();
 	}
+	
+	public String getMethodExecutionClassName() {
+		MethodExecution methodExecution = occurrencePoint.getMethodExecution();
+		return Trace.getDeclaringType(methodExecution.getSignature(), methodExecution.isConstructor());
+	}
 
 	public String getMethodSignature() {
 		return occurrencePoint.getMethodExecution().getCallerSideSignature();
diff --git a/org.ntlab.traceCollector/src/org/ntlab/traceCollector/tracer/trace/TraceJSON.java b/org.ntlab.traceCollector/src/org/ntlab/traceCollector/tracer/trace/TraceJSON.java
index 5161799..71608fc 100644
--- a/org.ntlab.traceCollector/src/org/ntlab/traceCollector/tracer/trace/TraceJSON.java
+++ b/org.ntlab.traceCollector/src/org/ntlab/traceCollector/tracer/trace/TraceJSON.java
@@ -1006,31 +1006,58 @@
 			Statement statement = statements.get(i);
 			if (statement instanceof FieldAccess) {
 				FieldAccess fa = (FieldAccess)statement;
-				startAliasList.add(new Alias(fa.getContainerObjId(), tp, Alias.OCCURRENCE_EXP_CONTAINER));
-				startAliasList.add(new Alias(fa.getValueObjId(), tp, Alias.OCCURRENCE_EXP_FIELD));
+				String objId = fa.getContainerObjId();
+				if (!("0".equals(objId))) {
+					startAliasList.add(new Alias(objId, tp, Alias.OCCURRENCE_EXP_CONTAINER));	
+				}
+				objId = fa.getValueObjId();
+				if ((!"0".equals(objId))) {
+					startAliasList.add(new Alias(objId, tp, Alias.OCCURRENCE_EXP_FIELD));	
+				}
 			} else if (statement instanceof FieldUpdate) {
 				FieldUpdate fu = (FieldUpdate)statement;
-				startAliasList.add(new Alias(fu.getContainerObjId(), tp, Alias.OCCURRENCE_EXP_CONTAINER));
-				startAliasList.add(new Alias(fu.getValueObjId(), tp, Alias.OCCURRENCE_EXP_FIELD));
+				String objId = fu.getContainerObjId();
+				if ((!"0".equals(objId))) {
+					startAliasList.add(new Alias(objId, tp, Alias.OCCURRENCE_EXP_CONTAINER));	
+				}
+				objId = fu.getValueObjId();
+				if ((!"0".equals(objId))) {
+					startAliasList.add(new Alias(objId, tp, Alias.OCCURRENCE_EXP_FIELD));	
+				}
 			} else if (statement instanceof ArrayAccess) {
 				String valueObjId = ((ArrayAccess)statement).getValueObjectId();
-				startAliasList.add(new Alias(valueObjId, tp, Alias.OCCURRENCE_EXP_ARRAY));
+				if (!("0".equals(valueObjId))) {
+					startAliasList.add(new Alias(valueObjId, tp, Alias.OCCURRENCE_EXP_ARRAY));	
+				}
 			} else if (statement instanceof ArrayUpdate) {
 				String valueObjId = ((ArrayUpdate)statement).getValueObjectId();
-				startAliasList.add(new Alias(valueObjId, tp, Alias.OCCURRENCE_EXP_ARRAY));
+				if (!("0".equals(valueObjId))) {
+					startAliasList.add(new Alias(valueObjId, tp, Alias.OCCURRENCE_EXP_ARRAY));	
+				}
 			} else if (statement instanceof ArrayCreate) {
 				String valueObjId = ((ArrayAccess)statement).getValueObjectId();
-				startAliasList.add(new Alias(valueObjId, tp, Alias.OCCURRENCE_EXP_RETURN));
+				if (!("0".equals(valueObjId))) {
+					startAliasList.add(new Alias(valueObjId, tp, Alias.OCCURRENCE_EXP_RETURN));	
+				}
 			} else if (statement instanceof MethodInvocation) {
 				MethodExecution calledMe = ((MethodInvocation)statement).getCalledMethodExecution();
-				startAliasList.add(new Alias(calledMe.getThisObjId(), tp, Alias.OCCURRENCE_EXP_RECEIVER));
+				String thisObjId = calledMe.getThisObjId();
+				if (!("0".equals(thisObjId))) {
+					startAliasList.add(new Alias(thisObjId, tp, Alias.OCCURRENCE_EXP_RECEIVER));	
+				}
 				List<ObjectReference> args = calledMe.getArguments();
 				for (int j = 0; j < args.size(); j++) {
-					startAliasList.add(new Alias(args.get(j).getId(), tp, (j + Alias.OCCURRENCE_EXP_FIRST_ARG)));
+					String argValueId = args.get(j).getId();
+					if (!("0".equals(argValueId))) {
+						startAliasList.add(new Alias(argValueId, tp, (j + Alias.OCCURRENCE_EXP_FIRST_ARG)));	
+					}
 				}
 				ObjectReference returnValue = calledMe.getReturnValue();
 				if (returnValue != null) {
-					startAliasList.add(new Alias(returnValue.getId(), tp, Alias.OCCURRENCE_EXP_RETURN));
+					String returnValueId = returnValue.getId();
+					if (!("0".equals(returnValueId))) {
+						startAliasList.add(new Alias(returnValueId, tp, Alias.OCCURRENCE_EXP_RETURN));
+					}
 				}
 			}
 		}