Index: lams_common/conf/hibernate/mappings/org/lamsfoundation/lams/learningdesign/Activity.hbm.xml
===================================================================
diff -u -rf05ccd126e7f4ea7377290ec65a2c39b3c7d08f9 -rd3e6f7950ebe3d12cc3f67bbe471fd6e1f7e6c60
--- lams_common/conf/hibernate/mappings/org/lamsfoundation/lams/learningdesign/Activity.hbm.xml	(.../Activity.hbm.xml)	(revision f05ccd126e7f4ea7377290ec65a2c39b3c7d08f9)
+++ lams_common/conf/hibernate/mappings/org/lamsfoundation/lams/learningdesign/Activity.hbm.xml	(.../Activity.hbm.xml)	(revision d3e6f7950ebe3d12cc3f67bbe471fd6e1f7e6c60)
@@ -64,38 +64,20 @@
    	</property>
     <property name="libraryActivityUiImage" type="java.lang.String" column="library_activity_ui_image" length="255">
         <meta attribute="field-description">@hibernate.property column="library_activity_ui_image" length="255"</meta>    
-    </property>    
-    
+    </property>
 
     <!-- Associations -->
+    <one-to-one name="transitionTo" class="org.lamsfoundation.lams.learningdesign.Transition" property-ref="activityByToActivityId"/>
+    <one-to-one name="transitionFrom" class="org.lamsfoundation.lams.learningdesign.Transition" property-ref="activityByFromActivityId"/>
     
     <!-- bi-directional many-to-one association to LearningLibrary -->
     <many-to-one name="learningLibrary" class="org.lamsfoundation.lams.learningdesign.LearningLibrary">
         <meta attribute="field-description">@hibernate.column name="learning_library_id"         
         </meta>
         <column name="learning_library_id" />
     </many-to-one>
+   
     
-    <!-- bi-directional one-to-many association to Transition -->
-    <set name="transitionsByToActivityId" lazy="false" inverse="true" cascade="none">
-        <meta attribute="field-description">@hibernate.set lazy="false" inverse="true" cascade="none" 
-        						            @hibernate.collection-key column="to_activity_id"
-        						            @hibernate.collection-one-to-many class="org.lamsfoundation.lams.learningdesign.Transition"
-        </meta>
-        <key><column name="to_activity_id" /></key>
-        <one-to-many class="org.lamsfoundation.lams.learningdesign.Transition"/>
-    </set>
-    
-    <!-- bi-directional one-to-many association to Transition -->
-    <set name="transitionsByFromActivityId" lazy="false" inverse="true" cascade="none" >
-        <meta attribute="field-description">@hibernate.set lazy="false" inverse="true" cascade="none"
-        							        @hibernate.collection-key column="from_activity_id"
-        							        @hibernate.collection-one-to-many class="org.lamsfoundation.lams.learningdesign.Transition"
-        </meta>
-        <key><column name="from_activity_id" /></key>
-        <one-to-many class="org.lamsfoundation.lams.learningdesign.Transition"/>
-    </set>
-    
     <!-- bi-directional many-to-one association to Activity -->
     <many-to-one name="parentActivity" class="org.lamsfoundation.lams.learningdesign.Activity">
         <meta attribute="field-description">@hibernate.column name="parent_activity_id"         
Index: lams_common/conf/hibernate/mappings/org/lamsfoundation/lams/learningdesign/Transition.hbm.xml
===================================================================
diff -u -r2db1c52567bf8f79ccb7589d1d8785be4ed1118c -rd3e6f7950ebe3d12cc3f67bbe471fd6e1f7e6c60
--- lams_common/conf/hibernate/mappings/org/lamsfoundation/lams/learningdesign/Transition.hbm.xml	(.../Transition.hbm.xml)	(revision 2db1c52567bf8f79ccb7589d1d8785be4ed1118c)
+++ lams_common/conf/hibernate/mappings/org/lamsfoundation/lams/learningdesign/Transition.hbm.xml	(.../Transition.hbm.xml)	(revision d3e6f7950ebe3d12cc3f67bbe471fd6e1f7e6c60)
@@ -91,31 +91,21 @@
     <!-- Associations -->
   
     <!-- bi-directional many-to-one association to Activity -->
-    <many-to-one
-        name="activityByToActivityId"
-        class="org.lamsfoundation.lams.learningdesign.Activity"
-        not-null="true"
-    >
-        <meta attribute="field-description">
-           @hibernate.many-to-one
-            not-null="true"
-           @hibernate.column name="to_activity_id"         
+    <many-to-one name="activityByToActivityId" class="org.lamsfoundation.lams.learningdesign.Activity" unique="true">
+        <meta attribute="field-description">@hibernate.many-to-one unique="true" 
+        									@hibernate.column name="to_activity_id"         
         </meta>
         <column name="to_activity_id" />
     </many-to-one>
+    
     <!-- bi-directional many-to-one association to Activity -->
-    <many-to-one
-        name="activityByFromActivityId"
-        class="org.lamsfoundation.lams.learningdesign.Activity"
-        not-null="true"
-    >
-        <meta attribute="field-description">
-           @hibernate.many-to-one
-            not-null="true"
-           @hibernate.column name="from_activity_id"         
+    <many-to-one name="activityByFromActivityId" class="org.lamsfoundation.lams.learningdesign.Activity" unique="true">
+        <meta attribute="field-description">@hibernate.many-to-one unique="true"
+        							        @hibernate.column name="from_activity_id"         
         </meta>
         <column name="from_activity_id" />
     </many-to-one>
+    
     <!-- bi-directional many-to-one association to LearningDesign -->
     <many-to-one
         name="learningDesign"
Index: lams_common/src/java/org/lamsfoundation/lams/learningdesign/Activity.java
===================================================================
diff -u -r701298e4804b6e63459ae7ce8fe82ae1765a3a82 -rd3e6f7950ebe3d12cc3f67bbe471fd6e1f7e6c60
--- lams_common/src/java/org/lamsfoundation/lams/learningdesign/Activity.java	(.../Activity.java)	(revision 701298e4804b6e63459ae7ce8fe82ae1765a3a82)
+++ lams_common/src/java/org/lamsfoundation/lams/learningdesign/Activity.java	(.../Activity.java)	(revision d3e6f7950ebe3d12cc3f67bbe471fd6e1f7e6c60)
@@ -2,7 +2,6 @@
 
 import java.io.Serializable;
 import java.util.Date;
-import java.util.Set;
 import org.apache.commons.lang.builder.EqualsBuilder;
 import org.apache.commons.lang.builder.HashCodeBuilder;
 import org.apache.commons.lang.builder.ToStringBuilder;
@@ -81,11 +80,11 @@
 	private Integer activityTypeId;
 
 	/** persistent field */
-	private Set transitionsByToActivityId;
-
-	/** persistent field */
-	private Set transitionsByFromActivityId;
+	private Transition transitionTo; 
 	
+	/** persistent field */
+	private Transition transitionFrom;
+		
 	/** full constructor */
 	public Activity(
 			Long activityId,
@@ -102,8 +101,9 @@
 			org.lamsfoundation.lams.learningdesign.Activity parentActivity,
 			org.lamsfoundation.lams.learningdesign.LearningDesign learningDesign,
 			org.lamsfoundation.lams.learningdesign.Grouping grouping,
-			Integer activityTypeId, Set transitionsByToActivityId,
-			Set transitionsByFromActivityId) {
+			Integer activityTypeId, 
+			Transition transitionTo,
+			Transition transitionFrom) {
 		this.activityId = activityId;
 		this.id = id;
 		this.description = description;
@@ -119,8 +119,8 @@
 		this.learningDesign = learningDesign;
 		this.grouping = grouping;
 		this.activityTypeId = activityTypeId;
-		this.transitionsByToActivityId = transitionsByToActivityId;
-		this.transitionsByFromActivityId = transitionsByFromActivityId;
+		this.transitionTo = transitionTo;
+		this.transitionFrom = transitionFrom;
 	}
 
 	/** default constructor */
@@ -137,8 +137,9 @@
 			org.lamsfoundation.lams.learningdesign.Activity parentActivity,
 			org.lamsfoundation.lams.learningdesign.LearningDesign learningDesign,
 			org.lamsfoundation.lams.learningdesign.Grouping grouping,
-			Integer activityTypeId, Set transitionsByToActivityId,
-			Set transitionsByFromActivityId) {
+			Integer activityTypeId,
+			Transition transitionTo,
+			Transition transitionFrom) {
 		this.activityId = activityId;
 		this.defineLater = defineLater;
 		this.createDateTime = createDateTime;
@@ -147,8 +148,8 @@
 		this.learningDesign = learningDesign;
 		this.grouping = grouping;
 		this.activityTypeId = activityTypeId;
-		this.transitionsByToActivityId = transitionsByToActivityId;
-		this.transitionsByFromActivityId = transitionsByFromActivityId;
+		this.transitionTo = transitionTo;
+		this.transitionFrom = transitionFrom;
 	}
 
 	/**
@@ -329,35 +330,6 @@
 	public void setActivityTypeId(Integer activityTypeId) {
 		this.activityTypeId = activityTypeId;
 	}
-
-	/**
-	 * @hibernate.set lazy="true" inverse="true" cascade="none"
-	 * @hibernate.collection-key column="to_activity_id"
-	 * @hibernate.collection-one-to-many class="org.lamsfoundation.lams.learningdesign.Transition"
-	 *  
-	 */
-	public Set getTransitionsByToActivityId() {
-		return this.transitionsByToActivityId;
-	}
-
-	public void setTransitionsByToActivityId(Set transitionsByToActivityId) {
-		this.transitionsByToActivityId = transitionsByToActivityId;
-	}
-
-	/**
-	 * @hibernate.set lazy="true" inverse="true" cascade="none"
-	 * @hibernate.collection-key column="from_activity_id"
-	 * @hibernate.collection-one-to-many class="org.lamsfoundation.lams.learningdesign.Transition"
-	 *  
-	 */
-	public Set getTransitionsByFromActivityId() {
-		return this.transitionsByFromActivityId;
-	}
-
-	public void setTransitionsByFromActivityId(Set transitionsByFromActivityId) {
-		this.transitionsByFromActivityId = transitionsByFromActivityId;
-	}
-
 	public String toString() {
 		return new ToStringBuilder(this).append("activityId", getActivityId())
 				.toString();
@@ -392,4 +364,28 @@
 	public void setLibraryActivityUiImage(String libraryActivityUiImage) {
 		this.libraryActivityUiImage = libraryActivityUiImage;
 	}	
+	/**
+	 * @return Returns the transitionFrom.
+	 */
+	public Transition getTransitionFrom() {
+		return transitionFrom;
+	}
+	/**
+	 * @param transitionFrom The transitionFrom to set.
+	 */
+	public void setTransitionFrom(Transition transitionFrom) {
+		this.transitionFrom = transitionFrom;
+	}
+	/**
+	 * @return Returns the transitionTo.
+	 */
+	public Transition getTransitionTo() {
+		return transitionTo;
+	}
+	/**
+	 * @param transitionTo The transitionTo to set.
+	 */
+	public void setTransitionTo(Transition transitionTo) {
+		this.transitionTo = transitionTo;
+	}
 }
\ No newline at end of file
Index: lams_common/src/java/org/lamsfoundation/lams/learningdesign/ComplexActivity.java
===================================================================
diff -u -rac6e6942d257c6266f4c38eef12192dea38cc73a -rd3e6f7950ebe3d12cc3f67bbe471fd6e1f7e6c60
--- lams_common/src/java/org/lamsfoundation/lams/learningdesign/ComplexActivity.java	(.../ComplexActivity.java)	(revision ac6e6942d257c6266f4c38eef12192dea38cc73a)
+++ lams_common/src/java/org/lamsfoundation/lams/learningdesign/ComplexActivity.java	(.../ComplexActivity.java)	(revision d3e6f7950ebe3d12cc3f67bbe471fd6e1f7e6c60)
@@ -29,13 +29,14 @@
 			Activity parentActivity,
 			LearningDesign learningDesign,
 			Grouping grouping,
-			Integer activityTypeId, Set transitionsByToActivityId,
-			Set transitionsByFromActivityId, Set activities) {
+			Integer activityTypeId, 
+			Transition transitionTo,
+			Transition transitionFrom,
+			Set activities) {
 		super(activityId, id, description, title, xcoord, ycoord, orderId,
 				defineLater, createDateTime, offlineInstructions,
 				learningLibrary, parentActivity, learningDesign, grouping,
-				activityTypeId, transitionsByToActivityId,
-				transitionsByFromActivityId);
+				activityTypeId, transitionTo,transitionFrom);
 		this.activities = activities;
 	}
 
@@ -53,11 +54,12 @@
 			Activity parentActivity,
 			LearningDesign learningDesign,
 			Grouping grouping,
-			Integer activityTypeId, Set transitionsByToActivityId,
-			Set transitionsByFromActivityId, Set activities) {
+			Integer activityTypeId, 
+			Transition transitionTo,
+			Transition transitionFrom,Set activities) {
 		super(activityId, defineLater, createDateTime, learningLibrary,
 				parentActivity, learningDesign, grouping, activityTypeId,
-				transitionsByToActivityId, transitionsByFromActivityId);
+				transitionTo,transitionFrom);
 		this.activities = activities;
 	}
 
Index: lams_common/src/java/org/lamsfoundation/lams/learningdesign/GateActivity.java
===================================================================
diff -u -r19c9010eff6be2e29657beed94349a978088650f -rd3e6f7950ebe3d12cc3f67bbe471fd6e1f7e6c60
--- lams_common/src/java/org/lamsfoundation/lams/learningdesign/GateActivity.java	(.../GateActivity.java)	(revision 19c9010eff6be2e29657beed94349a978088650f)
+++ lams_common/src/java/org/lamsfoundation/lams/learningdesign/GateActivity.java	(.../GateActivity.java)	(revision d3e6f7950ebe3d12cc3f67bbe471fd6e1f7e6c60)
@@ -35,8 +35,8 @@
             org.lamsfoundation.lams.learningdesign.LearningDesign learningDesign,
             org.lamsfoundation.lams.learningdesign.Grouping grouping,
             Integer activityTypeId,
-            java.util.Set transitionsByToActivityId,
-            java.util.Set transitionsByFromActivityId,
+            Transition transitionTo,
+            Transition transitionFrom,
             Integer gateActivityLevelId)
     {
         super(activityId,
@@ -54,8 +54,8 @@
                 learningDesign,
                 grouping,
                 activityTypeId,
-                transitionsByToActivityId,
-                transitionsByFromActivityId);
+                transitionTo,
+				transitionFrom);
         this.gateActivityLevelId = gateActivityLevelId;
     }
     
@@ -73,8 +73,8 @@
             org.lamsfoundation.lams.learningdesign.LearningDesign learningDesign,
             org.lamsfoundation.lams.learningdesign.Grouping grouping,
             Integer activityTypeId,
-            java.util.Set transitionsByToActivityId,
-            java.util.Set transitionsByFromActivityId,
+            Transition transitionTo,
+            Transition transitionFrom,
             Integer gateActivityLevelId)
     {
         super(activityId,
@@ -85,8 +85,8 @@
                 learningDesign,
                 grouping,
                 activityTypeId,
-                transitionsByToActivityId,
-                transitionsByFromActivityId);
+                transitionTo,
+				transitionFrom);
         this.gateActivityLevelId = gateActivityLevelId;
     }
     
Index: lams_common/src/java/org/lamsfoundation/lams/learningdesign/GroupingActivity.java
===================================================================
diff -u -r19c9010eff6be2e29657beed94349a978088650f -rd3e6f7950ebe3d12cc3f67bbe471fd6e1f7e6c60
--- lams_common/src/java/org/lamsfoundation/lams/learningdesign/GroupingActivity.java	(.../GroupingActivity.java)	(revision 19c9010eff6be2e29657beed94349a978088650f)
+++ lams_common/src/java/org/lamsfoundation/lams/learningdesign/GroupingActivity.java	(.../GroupingActivity.java)	(revision d3e6f7950ebe3d12cc3f67bbe471fd6e1f7e6c60)
@@ -29,8 +29,8 @@
             org.lamsfoundation.lams.learningdesign.LearningDesign learningDesign, 
             org.lamsfoundation.lams.learningdesign.Grouping grouping, 
             Integer activityTypeId,  
-            java.util.Set transitionsByToActivityId, 
-            java.util.Set transitionsByFromActivityId,
+            Transition transitionTo,
+            Transition transitionFrom,
             Grouping createGrouping)
     {
         super(activityId, 
@@ -48,8 +48,8 @@
                 learningDesign, 
                 grouping, 
                 activityTypeId, 
-                transitionsByToActivityId, 
-                transitionsByFromActivityId);
+                transitionTo,
+				transitionFrom);
         this.createGrouping = createGrouping;
     }
     
@@ -67,8 +67,8 @@
             org.lamsfoundation.lams.learningdesign.LearningDesign learningDesign,
             org.lamsfoundation.lams.learningdesign.Grouping grouping,
             Integer activityTypeId,
-            java.util.Set transitionsByToActivityId,
-            java.util.Set transitionsByFromActivityId,
+            Transition transitionTo,
+            Transition transitionFrom,
             Grouping createGrouping)
     {
         super(activityId,
@@ -79,8 +79,8 @@
                 learningDesign,
                 grouping,
                 activityTypeId,
-                transitionsByToActivityId,
-                transitionsByFromActivityId);
+                transitionTo,
+				transitionFrom);
         this.createGrouping = createGrouping;
     }
     
Index: lams_common/src/java/org/lamsfoundation/lams/learningdesign/OptionsActivity.java
===================================================================
diff -u -r701298e4804b6e63459ae7ce8fe82ae1765a3a82 -rd3e6f7950ebe3d12cc3f67bbe471fd6e1f7e6c60
--- lams_common/src/java/org/lamsfoundation/lams/learningdesign/OptionsActivity.java	(.../OptionsActivity.java)	(revision 701298e4804b6e63459ae7ce8fe82ae1765a3a82)
+++ lams_common/src/java/org/lamsfoundation/lams/learningdesign/OptionsActivity.java	(.../OptionsActivity.java)	(revision d3e6f7950ebe3d12cc3f67bbe471fd6e1f7e6c60)
@@ -31,8 +31,8 @@
             LearningDesign learningDesign, 
             Grouping grouping, 
             Integer activityTypeId,  
-            java.util.Set transitionsByToActivityId, 
-            java.util.Set transitionsByFromActivityId,
+            Transition transitionTo,
+            Transition transitionFrom,
             java.util.Set activities, 
             Integer maxNumberOfOptions, 
             Integer minNumberOfOptions) {
@@ -51,8 +51,8 @@
                 learningDesign, 
                 grouping, 
                 activityTypeId,  
-                transitionsByToActivityId,
-                transitionsByFromActivityId, 
+                transitionTo,
+				transitionFrom,
                 activities);
         this.maxNumberOfOptions = maxNumberOfOptions;
         this.minNumberOfOptions = minNumberOfOptions;
@@ -72,8 +72,8 @@
             org.lamsfoundation.lams.learningdesign.LearningDesign learningDesign, 
             org.lamsfoundation.lams.learningdesign.Grouping grouping, 
             Integer activityTypeId,  
-            java.util.Set transitionsByToActivityId, 
-            java.util.Set transitionsByFromActivityId, 
+            Transition transitionTo,
+            Transition transitionFrom,
             java.util.Set activities) {
       super(activityId, 
               defineLater, 
@@ -83,8 +83,8 @@
               learningDesign, 
               grouping, 
               activityTypeId, 
-              transitionsByToActivityId, 
-              transitionsByFromActivityId, 
+              transitionTo,
+              transitionFrom,
               activities);
     }
 
Index: lams_common/src/java/org/lamsfoundation/lams/learningdesign/ParallelActivity.java
===================================================================
diff -u -r701298e4804b6e63459ae7ce8fe82ae1765a3a82 -rd3e6f7950ebe3d12cc3f67bbe471fd6e1f7e6c60
--- lams_common/src/java/org/lamsfoundation/lams/learningdesign/ParallelActivity.java	(.../ParallelActivity.java)	(revision 701298e4804b6e63459ae7ce8fe82ae1765a3a82)
+++ lams_common/src/java/org/lamsfoundation/lams/learningdesign/ParallelActivity.java	(.../ParallelActivity.java)	(revision d3e6f7950ebe3d12cc3f67bbe471fd6e1f7e6c60)
@@ -25,8 +25,8 @@
             org.lamsfoundation.lams.learningdesign.LearningDesign learningDesign, 
             org.lamsfoundation.lams.learningdesign.Grouping grouping, 
             Integer activityTypeId,  
-            java.util.Set transitionsByToActivityId, 
-            java.util.Set transitionsByFromActivityId,
+            Transition transitionTo,
+            Transition transitionFrom,
             java.util.Set activities) {
         super(activityId, 
                 id, 
@@ -43,8 +43,8 @@
                 learningDesign, 
                 grouping, 
                 activityTypeId,  
-                transitionsByToActivityId,
-                transitionsByFromActivityId, 
+                transitionTo,
+				transitionFrom,
                 activities);
     }
 
@@ -61,8 +61,8 @@
             org.lamsfoundation.lams.learningdesign.LearningDesign learningDesign, 
             org.lamsfoundation.lams.learningdesign.Grouping grouping, 
             Integer activityTypeId,  
-            java.util.Set transitionsByToActivityId, 
-            java.util.Set transitionsByFromActivityId, 
+            Transition transitionTo,
+            Transition transitionFrom,
             java.util.Set activities) {
       super(activityId, 
               defineLater, 
@@ -72,8 +72,8 @@
               learningDesign, 
               grouping, 
               activityTypeId, 
-              transitionsByToActivityId, 
-              transitionsByFromActivityId, 
+              transitionTo,
+			  transitionFrom,
               activities);
     }
 
Index: lams_common/src/java/org/lamsfoundation/lams/learningdesign/PermissionGateActivity.java
===================================================================
diff -u -r19c9010eff6be2e29657beed94349a978088650f -rd3e6f7950ebe3d12cc3f67bbe471fd6e1f7e6c60
--- lams_common/src/java/org/lamsfoundation/lams/learningdesign/PermissionGateActivity.java	(.../PermissionGateActivity.java)	(revision 19c9010eff6be2e29657beed94349a978088650f)
+++ lams_common/src/java/org/lamsfoundation/lams/learningdesign/PermissionGateActivity.java	(.../PermissionGateActivity.java)	(revision d3e6f7950ebe3d12cc3f67bbe471fd6e1f7e6c60)
@@ -26,8 +26,8 @@
             org.lamsfoundation.lams.learningdesign.LearningDesign learningDesign,
             org.lamsfoundation.lams.learningdesign.Grouping grouping,
             Integer activityTypeId,
-            java.util.Set transitionsByToActivityId,
-            java.util.Set transitionsByFromActivityId,
+            Transition transitionTo,
+            Transition transitionFrom,
             Integer gateActivityLevelId)
     {
         super(activityId,
@@ -45,8 +45,8 @@
                 learningDesign,
                 grouping,
                 activityTypeId,
-                transitionsByToActivityId,
-                transitionsByFromActivityId,
+                transitionTo,
+				transitionFrom,
                 gateActivityLevelId);
     }
     
@@ -64,8 +64,8 @@
             org.lamsfoundation.lams.learningdesign.LearningDesign learningDesign,
             org.lamsfoundation.lams.learningdesign.Grouping grouping,
             Integer activityTypeId,
-            java.util.Set transitionsByToActivityId,
-            java.util.Set transitionsByFromActivityId,
+            Transition transitionTo,
+            Transition transitionFrom,
             Integer gateActivityLevelId)
     {
         super(activityId,
@@ -76,8 +76,8 @@
                 learningDesign,
                 grouping,
                 activityTypeId,
-                transitionsByToActivityId,
-                transitionsByFromActivityId,
+                transitionTo,
+				transitionFrom,
                 gateActivityLevelId);
     }
     
Index: lams_common/src/java/org/lamsfoundation/lams/learningdesign/ScheduleGateActivity.java
===================================================================
diff -u -r19c9010eff6be2e29657beed94349a978088650f -rd3e6f7950ebe3d12cc3f67bbe471fd6e1f7e6c60
--- lams_common/src/java/org/lamsfoundation/lams/learningdesign/ScheduleGateActivity.java	(.../ScheduleGateActivity.java)	(revision 19c9010eff6be2e29657beed94349a978088650f)
+++ lams_common/src/java/org/lamsfoundation/lams/learningdesign/ScheduleGateActivity.java	(.../ScheduleGateActivity.java)	(revision d3e6f7950ebe3d12cc3f67bbe471fd6e1f7e6c60)
@@ -32,8 +32,8 @@
             org.lamsfoundation.lams.learningdesign.LearningDesign learningDesign,
             org.lamsfoundation.lams.learningdesign.Grouping grouping,
             Integer activityTypeId,
-            java.util.Set transitionsByToActivityId,
-            java.util.Set transitionsByFromActivityId,
+            Transition transitionTo,
+            Transition transitionFrom,
             Integer gateActivityLevelId,
             Date gateStartDateTime, 
             Date gateEndDateTime) {
@@ -52,8 +52,8 @@
                 learningDesign,
                 grouping,
                 activityTypeId,
-                transitionsByToActivityId,
-                transitionsByFromActivityId,
+                transitionTo,
+				transitionFrom,
                 gateActivityLevelId);
         this.gateStartDateTime = gateStartDateTime;
         this.gateEndDateTime = gateEndDateTime;
@@ -72,8 +72,8 @@
             org.lamsfoundation.lams.learningdesign.LearningDesign learningDesign,
             org.lamsfoundation.lams.learningdesign.Grouping grouping,
             Integer activityTypeId,
-            java.util.Set transitionsByToActivityId,
-            java.util.Set transitionsByFromActivityId,
+            Transition transitionTo,
+            Transition transitionFrom,
             Integer gateActivityLevelId,
             Date gateStartDateTime, 
             Date gateEndDateTime) {
@@ -85,8 +85,8 @@
                 learningDesign,
                 grouping,
                 activityTypeId,
-                transitionsByToActivityId,
-                transitionsByFromActivityId,
+                transitionTo,
+				transitionFrom,
                 gateActivityLevelId);
       this.gateStartDateTime = gateStartDateTime;
       this.gateEndDateTime = gateEndDateTime;
Index: lams_common/src/java/org/lamsfoundation/lams/learningdesign/SequenceActivity.java
===================================================================
diff -u -r19c9010eff6be2e29657beed94349a978088650f -rd3e6f7950ebe3d12cc3f67bbe471fd6e1f7e6c60
--- lams_common/src/java/org/lamsfoundation/lams/learningdesign/SequenceActivity.java	(.../SequenceActivity.java)	(revision 19c9010eff6be2e29657beed94349a978088650f)
+++ lams_common/src/java/org/lamsfoundation/lams/learningdesign/SequenceActivity.java	(.../SequenceActivity.java)	(revision d3e6f7950ebe3d12cc3f67bbe471fd6e1f7e6c60)
@@ -25,8 +25,8 @@
             org.lamsfoundation.lams.learningdesign.LearningDesign learningDesign, 
             org.lamsfoundation.lams.learningdesign.Grouping grouping, 
             Integer activityTypeId,  
-            java.util.Set transitionsByToActivityId, 
-            java.util.Set transitionsByFromActivityId,
+            Transition transitionTo,
+            Transition transitionFrom,
             java.util.Set activities) {
         super(activityId, 
                 id, 
@@ -43,8 +43,8 @@
                 learningDesign, 
                 grouping, 
                 activityTypeId,  
-                transitionsByToActivityId,
-                transitionsByFromActivityId, 
+                transitionTo,
+				transitionFrom,
                 activities);
     }
 
@@ -62,8 +62,8 @@
             org.lamsfoundation.lams.learningdesign.LearningDesign learningDesign, 
             org.lamsfoundation.lams.learningdesign.Grouping grouping, 
             Integer activityTypeId,  
-            java.util.Set transitionsByToActivityId, 
-            java.util.Set transitionsByFromActivityId, 
+            Transition transitionTo,
+            Transition transitionFrom,
             java.util.Set activities) {
       super(activityId, 
               defineLater, 
@@ -73,8 +73,8 @@
               learningDesign, 
               grouping, 
               activityTypeId, 
-              transitionsByToActivityId, 
-              transitionsByFromActivityId, 
+              transitionTo,
+			  transitionFrom,
               activities);
     }
 
Index: lams_common/src/java/org/lamsfoundation/lams/learningdesign/SimpleActivity.java
===================================================================
diff -u -r19c9010eff6be2e29657beed94349a978088650f -rd3e6f7950ebe3d12cc3f67bbe471fd6e1f7e6c60
--- lams_common/src/java/org/lamsfoundation/lams/learningdesign/SimpleActivity.java	(.../SimpleActivity.java)	(revision 19c9010eff6be2e29657beed94349a978088650f)
+++ lams_common/src/java/org/lamsfoundation/lams/learningdesign/SimpleActivity.java	(.../SimpleActivity.java)	(revision d3e6f7950ebe3d12cc3f67bbe471fd6e1f7e6c60)
@@ -1,9 +1,7 @@
 package org.lamsfoundation.lams.learningdesign;
 
-import org.lamsfoundation.lams.tool.Tool;
 import java.io.Serializable;
 import java.util.Date;
-import java.util.Set;
 import org.apache.commons.lang.builder.ToStringBuilder;
 
 
@@ -28,9 +26,8 @@
             org.lamsfoundation.lams.learningdesign.Activity parentActivity, 
             org.lamsfoundation.lams.learningdesign.LearningDesign learningDesign, 
             org.lamsfoundation.lams.learningdesign.Grouping grouping, 
-            Integer activityTypeId, Set transitionsByToActivityId, 
-            Set transitionsByFromActivityId)
-    {
+            Integer activityTypeId, Transition transitionTo,
+			Transition transitionFrom){
         super(activityId, 
                 id, 
                 description, 
@@ -46,8 +43,8 @@
                 learningDesign, 
                 grouping, 
                 activityTypeId, 
-                transitionsByToActivityId, 
-                transitionsByFromActivityId);
+                transitionTo,
+				transitionFrom);
     }
     
     /** default constructor */
@@ -64,9 +61,8 @@
             org.lamsfoundation.lams.learningdesign.LearningDesign learningDesign, 
             org.lamsfoundation.lams.learningdesign.Grouping grouping, 
             Integer activityTypeId, 
-            Set transitionsByToActivityId, 
-            Set transitionsByFromActivityId)
-    {
+            Transition transitionTo,
+			Transition transitionFrom){
         super(activityId, 
                 defineLater, 
                 createDateTime, 
@@ -75,8 +71,8 @@
                 learningDesign, 
                 grouping, 
                 activityTypeId, 
-                transitionsByToActivityId, 
-                transitionsByFromActivityId);
+                transitionTo,
+				transitionFrom);
     }
     
     public String toString()
Index: lams_common/src/java/org/lamsfoundation/lams/learningdesign/SynchGateActivity.java
===================================================================
diff -u -r19c9010eff6be2e29657beed94349a978088650f -rd3e6f7950ebe3d12cc3f67bbe471fd6e1f7e6c60
--- lams_common/src/java/org/lamsfoundation/lams/learningdesign/SynchGateActivity.java	(.../SynchGateActivity.java)	(revision 19c9010eff6be2e29657beed94349a978088650f)
+++ lams_common/src/java/org/lamsfoundation/lams/learningdesign/SynchGateActivity.java	(.../SynchGateActivity.java)	(revision d3e6f7950ebe3d12cc3f67bbe471fd6e1f7e6c60)
@@ -25,8 +25,8 @@
             org.lamsfoundation.lams.learningdesign.LearningDesign learningDesign, 
             org.lamsfoundation.lams.learningdesign.Grouping grouping, 
             Integer activityTypeId, 
-            java.util.Set transitionsByToActivityId, 
-            java.util.Set transitionsByFromActivityId,
+            Transition transitionTo,
+            Transition transitionFrom,
             Integer gateActivityLevelId) {
         super(activityId, 
                 id, 
@@ -43,8 +43,8 @@
                 learningDesign, 
                 grouping, 
                 activityTypeId,  
-                transitionsByToActivityId, 
-                transitionsByFromActivityId,
+                transitionTo,
+				transitionFrom,
                 gateActivityLevelId);
     }
 
@@ -61,8 +61,8 @@
             org.lamsfoundation.lams.learningdesign.LearningDesign learningDesign, 
             org.lamsfoundation.lams.learningdesign.Grouping grouping, 
             Integer activityTypeId, 
-            java.util.Set transitionsByToActivityId, 
-            java.util.Set transitionsByFromActivityId,
+            Transition transitionTo,
+            Transition transitionFrom,
             Integer gateActivityLevelId) {
       super(activityId, 
               defineLater, 
@@ -72,8 +72,8 @@
               learningDesign, 
               grouping, 
               activityTypeId,  
-              transitionsByToActivityId, 
-              transitionsByFromActivityId,
+              transitionTo,
+			  transitionFrom,
               gateActivityLevelId);
     }
 
Index: lams_common/src/java/org/lamsfoundation/lams/learningdesign/ToolActivity.java
===================================================================
diff -u -r760bc2e946bb1910e70b18f7354bd9c6a0d407ff -rd3e6f7950ebe3d12cc3f67bbe471fd6e1f7e6c60
--- lams_common/src/java/org/lamsfoundation/lams/learningdesign/ToolActivity.java	(.../ToolActivity.java)	(revision 760bc2e946bb1910e70b18f7354bd9c6a0d407ff)
+++ lams_common/src/java/org/lamsfoundation/lams/learningdesign/ToolActivity.java	(.../ToolActivity.java)	(revision d3e6f7950ebe3d12cc3f67bbe471fd6e1f7e6c60)
@@ -42,8 +42,8 @@
             org.lamsfoundation.lams.learningdesign.LearningDesign learningDesign,
             org.lamsfoundation.lams.learningdesign.Grouping grouping,
             Integer activityTypeId,
-            java.util.Set transitionsByToActivityId,
-            java.util.Set transitionsByFromActivityId,
+            Transition transitionTo,
+            Transition transitionFrom,
             Tool tool,
             Long toolContentId)
     {
@@ -62,8 +62,8 @@
                 learningDesign,
                 grouping,
                 activityTypeId,
-                transitionsByToActivityId,
-                transitionsByFromActivityId);
+                transitionTo,
+				transitionFrom);
         this.tool = tool;
         this.toolContentId = toolContentId;
     }
@@ -82,8 +82,8 @@
             org.lamsfoundation.lams.learningdesign.LearningDesign learningDesign,
             org.lamsfoundation.lams.learningdesign.Grouping grouping,
             Integer activityTypeId,
-            java.util.Set transitionsByToActivityId,
-            java.util.Set transitionsByFromActivityId,
+            Transition transitionTo,
+            Transition transitionFrom,
             Tool tool,
             Long toolContentId)
     {
@@ -95,8 +95,8 @@
                 learningDesign,
                 grouping,
                 activityTypeId,
-                transitionsByToActivityId,
-                transitionsByFromActivityId);
+                transitionTo,
+				transitionFrom);
         this.tool = tool;
         this.toolContentId = toolContentId;
     }