diff --git a/devicehandlers/AssemblyBase.h b/devicehandlers/AssemblyBase.h
index 353d5f89..6cac81b4 100644
--- a/devicehandlers/AssemblyBase.h
+++ b/devicehandlers/AssemblyBase.h
@@ -24,6 +24,13 @@
  * 1. check logic when active-> checkChildrenStateOn
  * 2. transition logic to change the mode -> commandChildren
  *
+ * Important:
+ *
+ * The implementation must call registerChild(object_id_t child)
+ * for all commanded children during initialization.
+ * The implementation must call the initialization function of the base class.
+ * (This will call the function in SubsystemBase)
+ *
  */
 class AssemblyBase: public SubsystemBase {
 public:
@@ -41,9 +48,6 @@ public:
 	virtual ~AssemblyBase();
 
 protected:
-
-    // SHOULDDO: Change that OVERWRITE_HEALTH may be returned
-    // (or return internalState directly?)
     /**
      * Command children to reach [mode,submode] combination
      * Can be done by setting #commandsOutstanding correctly,
@@ -68,6 +72,18 @@ protected:
     virtual ReturnValue_t checkChildrenStateOn(Mode_t wantedMode,
             Submode_t wantedSubmode) = 0;
 
+    /**
+     * Check whether a combination of mode and submode is valid.
+     *
+     * Ground Controller like precise return values from HasModesIF.
+     * So, please return any of them.
+     *
+     * @param mode The targeted mode
+     * @param submode The targeted submmode
+     * @return Any information why this combination is invalid from HasModesIF
+     * 			like HasModesIF::INVALID_SUBMODE.
+     * 			On success return HasReturnvaluesIF::RETURN_OK
+     */
     virtual ReturnValue_t isModeCombinationValid(Mode_t mode,
             Submode_t submode) = 0;
 
diff --git a/subsystem/SubsystemBase.cpp b/subsystem/SubsystemBase.cpp
index bcfa4b0e..565e0712 100644
--- a/subsystem/SubsystemBase.cpp
+++ b/subsystem/SubsystemBase.cpp
@@ -5,8 +5,7 @@
 
 SubsystemBase::SubsystemBase(object_id_t setObjectId, object_id_t parent,
 		Mode_t initialMode, uint16_t commandQueueDepth) :
-		SystemObject(setObjectId), mode(initialMode), submode(SUBMODE_NONE),
-		childrenChangedMode(false),
+		SystemObject(setObjectId), mode(initialMode),
 		commandQueue(QueueFactory::instance()->createMessageQueue(
 		        commandQueueDepth, CommandMessage::MAX_MESSAGE_SIZE)),
 		healthHelper(this, setObjectId), modeHelper(this), parentId(parent) {
@@ -167,16 +166,16 @@ MessageQueueId_t SubsystemBase::getCommandQueue() const {
 }
 
 ReturnValue_t SubsystemBase::initialize() {
-	MessageQueueId_t parentQueue = 0;
+	MessageQueueId_t parentQueue = MessageQueueIF::NO_QUEUE;
 	ReturnValue_t result = SystemObject::initialize();
 
 	if (result != RETURN_OK) {
 		return result;
 	}
 
-	if (parentId != 0) {
+	if (parentId != objects::NO_OBJECT) {
 		SubsystemBase *parent = objectManager->get<SubsystemBase>(parentId);
-		if (parent == NULL) {
+		if (parent == nullptr) {
 			return RETURN_FAILED;
 		}
 		parentQueue = parent->getCommandQueue();
diff --git a/subsystem/SubsystemBase.h b/subsystem/SubsystemBase.h
index b8e4f902..6b2e9b5f 100644
--- a/subsystem/SubsystemBase.h
+++ b/subsystem/SubsystemBase.h
@@ -37,6 +37,17 @@ public:
 
 	virtual MessageQueueId_t getCommandQueue() const override;
 
+	/**
+	 * Function to register the child objects.
+	 * Performs a checks if the child does implement HasHealthIF and/or HasModesIF
+	 *
+	 * 	Also adds them to the internal childrenMap.
+	 *
+	 * @param objectId
+	 * @return RETURN_OK if successful
+	 * 		   CHILD_DOESNT_HAVE_MODES if Child is no HasHealthIF and no HasModesIF
+	 * 		   COULD_NOT_INSERT_CHILD If the Child could not be added to the ChildrenMap
+	 */
 	ReturnValue_t registerChild(object_id_t objectId);
 
 	virtual ReturnValue_t initialize() override;
@@ -56,9 +67,9 @@ protected:
 
 	Mode_t mode;
 
-	Submode_t submode;
+	Submode_t submode = SUBMODE_NONE;
 
-	bool childrenChangedMode;
+	bool childrenChangedMode = false;
 
 	/**
 	 * Always check this against <=0, so you are robust against too many replies