diff --git a/ganttzk/src/main/java/org/zkoss/ganttz/data/GanttDiagramGraph.java b/ganttzk/src/main/java/org/zkoss/ganttz/data/GanttDiagramGraph.java
index 3152dc669..0b9751306 100644
--- a/ganttzk/src/main/java/org/zkoss/ganttz/data/GanttDiagramGraph.java
+++ b/ganttzk/src/main/java/org/zkoss/ganttz/data/GanttDiagramGraph.java
@@ -292,7 +292,6 @@ public class GanttDiagramGraph implements ICriticalPathCalculable<Task> {
         return result;
     }
 
-    @Override
     public List<Task> getTopLevelTasks() {
         return Collections.unmodifiableList(topLevelTasks);
     }
@@ -304,6 +303,22 @@ public class GanttDiagramGraph implements ICriticalPathCalculable<Task> {
         parentShrinkingEnforcer.enforce();
     }
 
+    @Override
+    public List<Task> getInitialTasks() {
+        List<Task> tasks = new ArrayList<Task>();
+
+        for (Task task : graph.vertexSet()) {
+            int dependencies = graph.inDegreeOf(task);
+            if ((dependencies == 0)
+                    || (dependencies == getNumberOfDependenciesByType(task,
+                            DependencyType.END_END))) {
+                tasks.add(task);
+            }
+        }
+
+        return tasks;
+    }
+
     @Override
     public Dependency getDependencyFrom(Task from, Task to) {
         return graph.getEdge(from, to);
@@ -332,7 +347,7 @@ public class GanttDiagramGraph implements ICriticalPathCalculable<Task> {
     }
 
     @Override
-    public List<Task> getBottomLevelTasks() {
+    public List<Task> getLatestTasks() {
         List<Task> tasks = new ArrayList<Task>();
 
         for (Task task : graph.vertexSet()) {
diff --git a/ganttzk/src/main/java/org/zkoss/ganttz/data/criticalpath/CriticalPathCalculator.java b/ganttzk/src/main/java/org/zkoss/ganttz/data/criticalpath/CriticalPathCalculator.java
index 3fa12a90f..75eef7e96 100644
--- a/ganttzk/src/main/java/org/zkoss/ganttz/data/criticalpath/CriticalPathCalculator.java
+++ b/ganttzk/src/main/java/org/zkoss/ganttz/data/criticalpath/CriticalPathCalculator.java
@@ -61,11 +61,11 @@ public class CriticalPathCalculator<T extends ITaskFundamentalProperties> {
     }
 
     private InitialNode<T> createBeginningOfProjectNode() {
-        return new InitialNode<T>(new HashSet<T>(graph.getTopLevelTasks()));
+        return new InitialNode<T>(new HashSet<T>(graph.getInitialTasks()));
     }
 
     private LastNode<T> createEndOfProjectNode() {
-        return new LastNode<T>(new HashSet<T>(graph.getBottomLevelTasks()));
+        return new LastNode<T>(new HashSet<T>(graph.getLatestTasks()));
     }
 
     private Map<T, Node<T>> createGraphNodes() {
diff --git a/ganttzk/src/main/java/org/zkoss/ganttz/data/criticalpath/ICriticalPathCalculable.java b/ganttzk/src/main/java/org/zkoss/ganttz/data/criticalpath/ICriticalPathCalculable.java
index 60f1b0187..991c74207 100644
--- a/ganttzk/src/main/java/org/zkoss/ganttz/data/criticalpath/ICriticalPathCalculable.java
+++ b/ganttzk/src/main/java/org/zkoss/ganttz/data/criticalpath/ICriticalPathCalculable.java
@@ -36,9 +36,9 @@ import org.zkoss.ganttz.data.Task;
  */
 public interface ICriticalPathCalculable<T extends ITaskFundamentalProperties> {
 
-    List<T> getTopLevelTasks();
+    List<T> getInitialTasks();
 
-    List<T> getBottomLevelTasks();
+    List<T> getLatestTasks();
 
     Set<T> getIncomingTasksFor(T task);
 
diff --git a/ganttzk/src/test/java/org/zkoss/ganttz/data/criticalpath/CriticalPathCalculatorTest.java b/ganttzk/src/test/java/org/zkoss/ganttz/data/criticalpath/CriticalPathCalculatorTest.java
index 40eaae29f..1761af56e 100644
--- a/ganttzk/src/test/java/org/zkoss/ganttz/data/criticalpath/CriticalPathCalculatorTest.java
+++ b/ganttzk/src/test/java/org/zkoss/ganttz/data/criticalpath/CriticalPathCalculatorTest.java
@@ -95,9 +95,9 @@ public class CriticalPathCalculatorTest {
 
         expect(diagramGraphExample.getTasks()).andReturn(listOfTasks)
                 .anyTimes();
-        expect(diagramGraphExample.getTopLevelTasks()).andReturn(listOfTasks)
+        expect(diagramGraphExample.getInitialTasks()).andReturn(listOfTasks)
                 .anyTimes();
-        expect(diagramGraphExample.getBottomLevelTasks())
+        expect(diagramGraphExample.getLatestTasks())
                 .andReturn(listOfTasks).anyTimes();
         expect(
                 diagramGraphExample.getDependencyFrom(
@@ -133,9 +133,9 @@ public class CriticalPathCalculatorTest {
 
         expect(diagramGraphExample.getTasks()).andReturn(listOfTasks)
                 .anyTimes();
-        expect(diagramGraphExample.getTopLevelTasks()).andReturn(listOfTasks)
+        expect(diagramGraphExample.getInitialTasks()).andReturn(listOfTasks)
                 .anyTimes();
-        expect(diagramGraphExample.getBottomLevelTasks())
+        expect(diagramGraphExample.getLatestTasks())
                 .andReturn(listOfTasks).anyTimes();
         expect(
                 diagramGraphExample.getDependencyFrom(
@@ -173,9 +173,9 @@ public class CriticalPathCalculatorTest {
 
         expect(diagramGraphExample.getTasks()).andReturn(listOfTasks)
                 .anyTimes();
-        expect(diagramGraphExample.getTopLevelTasks()).andReturn(
+        expect(diagramGraphExample.getInitialTasks()).andReturn(
                 Arrays.asList(task1)).anyTimes();
-        expect(diagramGraphExample.getBottomLevelTasks()).andReturn(
+        expect(diagramGraphExample.getLatestTasks()).andReturn(
                 Arrays.asList(subtask1)).anyTimes();
         expect(
                 diagramGraphExample.getDependencyFrom(
@@ -220,9 +220,9 @@ public class CriticalPathCalculatorTest {
 
         expect(diagramGraphExample.getTasks()).andReturn(listOfTasks)
                 .anyTimes();
-        expect(diagramGraphExample.getTopLevelTasks()).andReturn(
+        expect(diagramGraphExample.getInitialTasks()).andReturn(
                 Arrays.asList(task1, task2)).anyTimes();
-        expect(diagramGraphExample.getBottomLevelTasks()).andReturn(
+        expect(diagramGraphExample.getLatestTasks()).andReturn(
                 Arrays.asList(subtask1, subtask2)).anyTimes();
         expect(
                 diagramGraphExample.getDependencyFrom(
@@ -277,9 +277,9 @@ public class CriticalPathCalculatorTest {
 
         expect(diagramGraphExample.getTasks()).andReturn(listOfTasks)
                 .anyTimes();
-        expect(diagramGraphExample.getTopLevelTasks()).andReturn(
+        expect(diagramGraphExample.getInitialTasks()).andReturn(
                 Arrays.asList(task1, independentTask)).anyTimes();
-        expect(diagramGraphExample.getBottomLevelTasks()).andReturn(
+        expect(diagramGraphExample.getLatestTasks()).andReturn(
                 Arrays.asList(task2, independentTask)).anyTimes();
         expect(
                 diagramGraphExample.getDependencyFrom(
@@ -326,9 +326,9 @@ public class CriticalPathCalculatorTest {
 
         expect(diagramGraphExample.getTasks()).andReturn(listOfTasks)
                 .anyTimes();
-        expect(diagramGraphExample.getTopLevelTasks()).andReturn(
+        expect(diagramGraphExample.getInitialTasks()).andReturn(
                 Arrays.asList(task)).anyTimes();
-        expect(diagramGraphExample.getBottomLevelTasks()).andReturn(
+        expect(diagramGraphExample.getLatestTasks()).andReturn(
                 Arrays.asList(subtask1, subtask2)).anyTimes();
         expect(
                 diagramGraphExample.getDependencyFrom(
@@ -376,9 +376,9 @@ public class CriticalPathCalculatorTest {
 
         expect(diagramGraphExample.getTasks()).andReturn(listOfTasks)
                 .anyTimes();
-        expect(diagramGraphExample.getTopLevelTasks()).andReturn(
+        expect(diagramGraphExample.getInitialTasks()).andReturn(
                 Arrays.asList(task1, task2)).anyTimes();
-        expect(diagramGraphExample.getBottomLevelTasks()).andReturn(
+        expect(diagramGraphExample.getLatestTasks()).andReturn(
                 Arrays.asList(subtask1)).anyTimes();
         expect(
                 diagramGraphExample.getDependencyFrom(
@@ -430,9 +430,9 @@ public class CriticalPathCalculatorTest {
 
         expect(diagramGraphExample.getTasks()).andReturn(listOfTasks)
                 .anyTimes();
-        expect(diagramGraphExample.getTopLevelTasks()).andReturn(
+        expect(diagramGraphExample.getInitialTasks()).andReturn(
                 Arrays.asList(task)).anyTimes();
-        expect(diagramGraphExample.getBottomLevelTasks()).andReturn(
+        expect(diagramGraphExample.getLatestTasks()).andReturn(
                 Arrays.asList(finalTask)).anyTimes();
         expect(
                 diagramGraphExample.getDependencyFrom(
@@ -492,9 +492,9 @@ public class CriticalPathCalculatorTest {
 
         expect(diagramGraphExample.getTasks()).andReturn(listOfTasks)
                 .anyTimes();
-        expect(diagramGraphExample.getTopLevelTasks()).andReturn(
+        expect(diagramGraphExample.getInitialTasks()).andReturn(
                 Arrays.asList(task1, task2)).anyTimes();
-        expect(diagramGraphExample.getBottomLevelTasks()).andReturn(
+        expect(diagramGraphExample.getLatestTasks()).andReturn(
                 Arrays.asList(finalTask1, finalTask2)).anyTimes();
         expect(
                 diagramGraphExample.getDependencyFrom(
@@ -567,9 +567,9 @@ public class CriticalPathCalculatorTest {
 
         expect(diagramGraphExample.getTasks()).andReturn(listOfTasks)
                 .anyTimes();
-        expect(diagramGraphExample.getTopLevelTasks()).andReturn(
+        expect(diagramGraphExample.getInitialTasks()).andReturn(
                 Arrays.asList(task4, task6)).anyTimes();
-        expect(diagramGraphExample.getBottomLevelTasks()).andReturn(
+        expect(diagramGraphExample.getLatestTasks()).andReturn(
                 Arrays.asList(task10, modifiableTask)).anyTimes();
         expect(
                 diagramGraphExample.getDependencyFrom(
@@ -644,9 +644,9 @@ public class CriticalPathCalculatorTest {
 
         expect(diagramGraphExample.getTasks()).andReturn(listOfTasks)
                 .anyTimes();
-        expect(diagramGraphExample.getTopLevelTasks()).andReturn(
+        expect(diagramGraphExample.getInitialTasks()).andReturn(
                 Arrays.asList(task1)).anyTimes();
-        expect(diagramGraphExample.getBottomLevelTasks()).andReturn(
+        expect(diagramGraphExample.getLatestTasks()).andReturn(
                 Arrays.asList(task1, task2)).anyTimes();
 
         IDependency<ITaskFundamentalProperties> dependency = createDependency(
@@ -689,9 +689,9 @@ public class CriticalPathCalculatorTest {
 
         expect(diagramGraphExample.getTasks()).andReturn(listOfTasks)
                 .anyTimes();
-        expect(diagramGraphExample.getTopLevelTasks()).andReturn(
+        expect(diagramGraphExample.getInitialTasks()).andReturn(
                 Arrays.asList(task1)).anyTimes();
-        expect(diagramGraphExample.getBottomLevelTasks()).andReturn(
+        expect(diagramGraphExample.getLatestTasks()).andReturn(
                 Arrays.asList(subtask1, task2)).anyTimes();
 
         IDependency<ITaskFundamentalProperties> dependency = createDependency(
@@ -741,9 +741,9 @@ public class CriticalPathCalculatorTest {
 
         expect(diagramGraphExample.getTasks()).andReturn(listOfTasks)
                 .anyTimes();
-        expect(diagramGraphExample.getTopLevelTasks()).andReturn(
+        expect(diagramGraphExample.getInitialTasks()).andReturn(
                 Arrays.asList(task1, task2)).anyTimes();
-        expect(diagramGraphExample.getBottomLevelTasks()).andReturn(
+        expect(diagramGraphExample.getLatestTasks()).andReturn(
                 Arrays.asList(subtask1, subtask2)).anyTimes();
 
         IDependency<ITaskFundamentalProperties> dependency = createDependency(
@@ -804,9 +804,9 @@ public class CriticalPathCalculatorTest {
 
         expect(diagramGraphExample.getTasks()).andReturn(listOfTasks)
                 .anyTimes();
-        expect(diagramGraphExample.getTopLevelTasks()).andReturn(
+        expect(diagramGraphExample.getInitialTasks()).andReturn(
                 Arrays.asList(task1)).anyTimes();
-        expect(diagramGraphExample.getBottomLevelTasks()).andReturn(
+        expect(diagramGraphExample.getLatestTasks()).andReturn(
                 Arrays.asList(subtask1, subtask2, subtask3)).anyTimes();
 
         IDependency<ITaskFundamentalProperties> dependency = createDependency(