diff --git a/navalplanner-business/src/main/java/org/navalplanner/business/planner/entities/Task.java b/navalplanner-business/src/main/java/org/navalplanner/business/planner/entities/Task.java
index 5dc03afe1..f864c77ae 100644
--- a/navalplanner-business/src/main/java/org/navalplanner/business/planner/entities/Task.java
+++ b/navalplanner-business/src/main/java/org/navalplanner/business/planner/entities/Task.java
@@ -1,5 +1,7 @@
 package org.navalplanner.business.planner.entities;
 
+import java.util.List;
+
 import org.apache.commons.lang.Validate;
 import org.hibernate.validator.NotNull;
 import org.navalplanner.business.orders.entities.HoursGroup;
@@ -36,4 +38,14 @@ public class Task extends TaskElement {
         return hoursGroup.getWorkingHours();
     }
 
+    @Override
+    public boolean isLeaf() {
+        return true;
+    }
+
+    @Override
+    public List<TaskElement> getChildren() {
+        throw new UnsupportedOperationException();
+    }
+
 }
diff --git a/navalplanner-business/src/main/java/org/navalplanner/business/planner/entities/TaskElement.java b/navalplanner-business/src/main/java/org/navalplanner/business/planner/entities/TaskElement.java
index 744959c9c..2fb03ac30 100644
--- a/navalplanner-business/src/main/java/org/navalplanner/business/planner/entities/TaskElement.java
+++ b/navalplanner-business/src/main/java/org/navalplanner/business/planner/entities/TaskElement.java
@@ -3,6 +3,7 @@ package org.navalplanner.business.planner.entities;
 import java.util.Collections;
 import java.util.Date;
 import java.util.HashSet;
+import java.util.List;
 import java.util.Set;
 
 import org.apache.commons.lang.Validate;
@@ -83,4 +84,8 @@ public abstract class TaskElement {
         return id;
     }
 
+    public abstract boolean isLeaf();
+
+    public abstract List<TaskElement> getChildren();
+
 }
diff --git a/navalplanner-business/src/main/java/org/navalplanner/business/planner/entities/TaskGroup.java b/navalplanner-business/src/main/java/org/navalplanner/business/planner/entities/TaskGroup.java
index abfa15d72..ad2d408d2 100644
--- a/navalplanner-business/src/main/java/org/navalplanner/business/planner/entities/TaskGroup.java
+++ b/navalplanner-business/src/main/java/org/navalplanner/business/planner/entities/TaskGroup.java
@@ -13,13 +13,19 @@ public class TaskGroup extends TaskElement {
 
     private List<TaskElement> taskElements = new ArrayList<TaskElement>();
 
-    public List<TaskElement> getTaskElements() {
-        return Collections.unmodifiableList(taskElements);
-    }
-
     public void addTaskElement(TaskElement task) {
         Validate.notNull(task);
         taskElements.add(task);
     }
 
+    @Override
+    public List<TaskElement> getChildren() {
+        return Collections.unmodifiableList(taskElements);
+    }
+
+    @Override
+    public boolean isLeaf() {
+        return false;
+    }
+
 }
diff --git a/navalplanner-business/src/test/java/org/navalplanner/business/test/planner/entities/TaskGroupTest.java b/navalplanner-business/src/test/java/org/navalplanner/business/test/planner/entities/TaskGroupTest.java
index 7b292c3a6..d54b919dc 100644
--- a/navalplanner-business/src/test/java/org/navalplanner/business/test/planner/entities/TaskGroupTest.java
+++ b/navalplanner-business/src/test/java/org/navalplanner/business/test/planner/entities/TaskGroupTest.java
@@ -25,16 +25,16 @@ public class TaskGroupTest {
 
     @Test
     public void taskGroupHasManyTaskElements() {
-        List<TaskElement> tasks = taskGroup.getTaskElements();
+        List<TaskElement> tasks = taskGroup.getChildren();
         assertTrue("a task group has no task elements initially", tasks
                 .isEmpty());
         TaskElement child1 = new Task();
         taskGroup.addTaskElement(child1);
         TaskGroup child2 = new TaskGroup();
         taskGroup.addTaskElement(child2);
-        List<TaskElement> taskElements = taskGroup.getTaskElements();
+        List<TaskElement> taskElements = taskGroup.getChildren();
         assertThat(taskElements.size(), equalTo(2));
-        assertThat(taskGroup.getTaskElements(), equalTo(Arrays.asList(child1,
+        assertThat(taskGroup.getChildren(), equalTo(Arrays.asList(child1,
                 child2)));
     }
 
@@ -45,6 +45,6 @@ public class TaskGroupTest {
 
     @Test(expected = UnsupportedOperationException.class)
     public void taskElementsCollectionCannotBeModified() {
-        taskGroup.getTaskElements().set(0, null);
+        taskGroup.getChildren().set(0, null);
     }
 }
diff --git a/navalplanner-business/src/test/java/org/navalplanner/business/test/planner/services/TaskElementServiceTest.java b/navalplanner-business/src/test/java/org/navalplanner/business/test/planner/services/TaskElementServiceTest.java
index c8cbe43c7..2fba5bb02 100644
--- a/navalplanner-business/src/test/java/org/navalplanner/business/test/planner/services/TaskElementServiceTest.java
+++ b/navalplanner-business/src/test/java/org/navalplanner/business/test/planner/services/TaskElementServiceTest.java
@@ -141,7 +141,7 @@ public class TaskElementServiceTest {
         flushAndEvict(taskGroup);
         TaskGroup reloaded = (TaskGroup) taskElementService.findById(taskGroup
                 .getId());
-        List<TaskElement> taskElements = reloaded.getTaskElements();
+        List<TaskElement> taskElements = reloaded.getChildren();
         assertThat(taskElements.size(), equalTo(2));
         assertThat(taskElements.get(0).getId(), equalTo(child1.getId()));
         assertThat(taskElements.get(1).getId(), equalTo(child2.getId()));
@@ -161,14 +161,14 @@ public class TaskElementServiceTest {
         flushAndEvict(taskGroup);
         TaskGroup reloaded = (TaskGroup) taskElementService.findById(taskGroup
                 .getId());
-        assertThat(reloaded.getTaskElements().get(0)
+        assertThat(reloaded.getChildren().get(0)
                 .getDependenciesWithThisOrigin().size(), equalTo(1));
-        assertTrue(reloaded.getTaskElements().get(0)
+        assertTrue(reloaded.getChildren().get(0)
                 .getDependenciesWithThisDestination().isEmpty());
 
-        assertThat(reloaded.getTaskElements().get(1)
+        assertThat(reloaded.getChildren().get(1)
                 .getDependenciesWithThisDestination().size(), equalTo(1));
-        assertTrue(reloaded.getTaskElements().get(1)
+        assertTrue(reloaded.getChildren().get(1)
                 .getDependenciesWithThisOrigin().isEmpty());
     }
 
@@ -217,8 +217,8 @@ public class TaskElementServiceTest {
 
         assertThat(group.getOrderElement(),
                 equalTo((OrderElement) orderLineGroup));
-        assertThat(group.getTaskElements().size(), equalTo(1));
-        assertThat(group.getTaskElements().get(0).getOrderElement(),
+        assertThat(group.getChildren().size(), equalTo(1));
+        assertThat(group.getChildren().get(0).getOrderElement(),
                 equalTo((OrderElement) orderLine));
     }
 
@@ -249,10 +249,10 @@ public class TaskElementServiceTest {
 
         TaskGroup group = (TaskGroup) taskElement;
         assertThat(group.getOrderElement(), equalTo((OrderElement) orderLine));
-        assertThat(group.getTaskElements().size(), equalTo(2));
+        assertThat(group.getChildren().size(), equalTo(2));
 
-        Task child1 = (Task) group.getTaskElements().get(0);
-        Task child2 = (Task) group.getTaskElements().get(1);
+        Task child1 = (Task) group.getChildren().get(0);
+        Task child2 = (Task) group.getChildren().get(1);
 
         assertThat(child1.getOrderElement(), equalTo((OrderElement) orderLine));
         assertThat(child2.getOrderElement(), equalTo((OrderElement) orderLine));