diff --git a/src/org/ntlab/deltaViewer/CollaborationAliasCollector.java b/src/org/ntlab/deltaViewer/CollaborationAliasCollector.java
index 9f22d79..979f5f7 100644
--- a/src/org/ntlab/deltaViewer/CollaborationAliasCollector.java
+++ b/src/org/ntlab/deltaViewer/CollaborationAliasCollector.java
@@ -7,6 +7,7 @@
 
 import org.ntlab.deltaExtractor.Alias;
 import org.ntlab.deltaExtractor.IAliasCollector;
+import org.ntlab.featureExtractor.Extract;
 
 /**
  * CollaborationAliasCollector is IAliasCollector implementation class to merge aliasList in time stamp order.
@@ -37,15 +38,25 @@
 	/**
 	 * Merge other into aliasList(this) in time stamp order.
 	 * @param other�@IAliasCollector to be merged into the aliasList.
+	 * @param extract 
 	 */
-	public void merge(IAliasCollector other) {
+	public void merge(IAliasCollector other, Extract extract) {
 		List<Alias> otherAliasList = other.getAliasList();
 		otherAliasList = sortAliasListByTimeStamp(otherAliasList);
-		int otherIdx = 0; // Index of otherAliasList
-		int thisIdx = 0; // Index of thisAliasList
+		int otherIdx = 0; // Index in otherAliasList
+		int thisIdx = 0; // Index in thisAliasList
+		int thisOrgIdx = 0; // Index in the original thisAliasList
 		while(otherIdx < otherAliasList.size()) {
 			Alias otherAlias = otherAliasList.get(otherIdx);
 			if (thisIdx >= aliasList.size()) {
+				if (extract != null && extract.isToConnect() && otherIdx == 0) {
+					Alias thisPrevAlias = aliasList.get(aliasList.size() - 1);
+					if (!otherAlias.getMethodExecution().isStatic() && otherAlias.getMethodExecution().getCallerMethodExecution() != thisPrevAlias.getMethodExecution()) {
+						// Add a dummy alias to connect disjunct call hierarchies.
+						aliasList.add(new Alias(Alias.AliasType.RECEIVER, 0, otherAlias.getMethodExecution().getThisObjId(), thisPrevAlias.getOccurrencePoint()));
+						thisIdx++;
+					}
+				}
 				aliasList.add(otherAlias);
 				otherIdx++; thisIdx++;
 				continue;
@@ -53,16 +64,32 @@
 			
 			Alias thisAlias = aliasList.get(thisIdx);
 			if (otherAlias.equals(thisAlias)) {
-				otherIdx++; thisIdx++;
+				otherIdx++; thisIdx++; thisOrgIdx++;
 			} else {
 				long otherAliasTs = otherAlias.getTimeStamp();
 				long thisAliasTs = thisAlias.getTimeStamp();
 				
 				if (otherAliasTs < thisAliasTs) {
+					if (extract != null && extract.isToConnect() && otherIdx == 0 && thisIdx > 0) {
+						Alias thisPrevAlias = aliasList.get(thisIdx - 1);
+						if (!otherAlias.getMethodExecution().isStatic() && otherAlias.getMethodExecution().getCallerMethodExecution() != thisPrevAlias.getMethodExecution()) {
+							// Add a dummy alias to connect disjunct call hierarchies.
+							aliasList.add(thisIdx, new Alias(Alias.AliasType.RECEIVER, 0, otherAlias.getMethodExecution().getThisObjId(), thisPrevAlias.getOccurrencePoint()));
+							thisIdx++;
+						}
+					}
 					aliasList.add(thisIdx, otherAlias);
 					otherIdx++; thisIdx++;
 				} else if (otherAliasTs > thisAliasTs) {
-					thisIdx++;
+					if (extract != null && extract.isToConnect() && thisOrgIdx == 0 && otherIdx > 0) {
+						Alias otherPrevAlias = otherAliasList.get(otherIdx - 1);
+						if (!thisAlias.getMethodExecution().isStatic() && thisAlias.getMethodExecution().getCallerMethodExecution() != otherPrevAlias.getMethodExecution()) {
+							// Add a dummy alias to connect disjunct call hierarchies.
+							aliasList.add(thisIdx, new Alias(Alias.AliasType.RECEIVER, 0, thisAlias.getMethodExecution().getThisObjId(), otherPrevAlias.getOccurrencePoint()));
+							thisIdx++;
+						}
+					}
+					thisIdx++; thisOrgIdx++;
 				} else {
 					if (aliasList.contains(otherAlias)) {
 						otherIdx++;
@@ -74,6 +101,14 @@
 				}
 			}
 		}
+		if (extract != null && extract.isToConnect() && thisOrgIdx == 0 && otherIdx > 0 && thisIdx < aliasList.size()) {
+			Alias thisAlias = aliasList.get(thisIdx);
+			Alias otherPrevAlias = otherAliasList.get(otherIdx - 1);
+			if (!thisAlias.getMethodExecution().isStatic() && thisAlias.getMethodExecution().getCallerMethodExecution() != otherPrevAlias.getMethodExecution()) {
+				// Add a dummy alias to connect disjunct call hierarchies.
+				aliasList.add(thisIdx, new Alias(Alias.AliasType.RECEIVER, 0, thisAlias.getMethodExecution().getThisObjId(), otherPrevAlias.getOccurrencePoint()));
+			}
+		}
 	}
 	
 	/**