diff --git a/mindplot/src/main/javascript/commands/AddIconToTopicCommand.js b/mindplot/src/main/javascript/commands/AddIconToTopicCommand.js
index 2b3a556d..e764cee4 100644
--- a/mindplot/src/main/javascript/commands/AddIconToTopicCommand.js
+++ b/mindplot/src/main/javascript/commands/AddIconToTopicCommand.js
@@ -21,18 +21,18 @@ mindplot.commands.AddIconToTopicCommand = new Class({
     initialize: function(topicId, iconType) {
         $assert($defined(topicId), 'topicId can not be null');
         $assert(iconType, 'iconType can not be null');
-        this._objectsIds = topicId;
+        this._topicsIds = topicId;
         this._iconType = iconType;
     },
 
     execute: function(commandContext) {
-        var topic = commandContext.findTopics(this._objectsIds)[0];
+        var topic = commandContext.findTopics(this._topicsIds)[0];
         var iconImg = topic.addIcon(this._iconType, commandContext._designer);
         this._iconModel = iconImg.getModel();
     },
 
     undoExecute: function(commandContext) {
-        var topic = commandContext.findTopics(this._objectsIds)[0];
+        var topic = commandContext.findTopics(this._topicsIds)[0];
         topic.removeIcon(this._iconModel);
     }
 });
\ No newline at end of file
diff --git a/mindplot/src/main/javascript/commands/ChangeLinkToTopicCommand.js b/mindplot/src/main/javascript/commands/ChangeLinkToTopicCommand.js
index 1d1314f4..ef259057 100644
--- a/mindplot/src/main/javascript/commands/ChangeLinkToTopicCommand.js
+++ b/mindplot/src/main/javascript/commands/ChangeLinkToTopicCommand.js
@@ -20,13 +20,13 @@ mindplot.commands.ChangeLinkToTopicCommand = new Class({
     Extends:mindplot.Command,
     initialize: function(topicId, url) {
         $assert(topicId, 'topicId can not be null');
-        this._objectsIds = topicId;
+        this._topicsIds = topicId;
         this._url = url;
         this._id = mindplot.Command._nextUUID();
     },
 
     execute: function(commandContext) {
-        var topic = commandContext.findTopics(this._objectsIds)[0];
+        var topic = commandContext.findTopics(this._topicsIds)[0];
         if (topic.hasLink()) {
             var model = topic.getModel();
             var link = model.getLinks()[0];
@@ -37,7 +37,7 @@ mindplot.commands.ChangeLinkToTopicCommand = new Class({
     },
 
     undoExecute: function(commandContext) {
-        var topic = commandContext.findTopics(this._objectsIds)[0];
+        var topic = commandContext.findTopics(this._topicsIds)[0];
         if (this._oldtext) {
             topic.removeLink();
             topic.addLink(this._oldUrl);
diff --git a/mindplot/src/main/javascript/commands/ChangeNoteToTopicCommand.js b/mindplot/src/main/javascript/commands/ChangeNoteToTopicCommand.js
index d556a529..6c3ad86c 100644
--- a/mindplot/src/main/javascript/commands/ChangeNoteToTopicCommand.js
+++ b/mindplot/src/main/javascript/commands/ChangeNoteToTopicCommand.js
@@ -20,14 +20,14 @@ mindplot.commands.ChangeNoteToTopicCommand = new Class({
     Extends:mindplot.Command,
     initialize: function(topicId, text) {
         $assert(topicId, 'topicId can not be null');
-        this._objectsIds = topicId;
+        this._topicsIds = topicId;
         this._text = text;
         this._oldtext = null;
         this._id = mindplot.Command._nextUUID();
     },
 
      execute: function(commandContext) {
-        var topic = commandContext.findTopics(this._objectsIds)[0];
+        var topic = commandContext.findTopics(this._topicsIds)[0];
         if (topic.hasNote()) {
             var model = topic.getModel();
             var notes = model.getNotes()[0];
@@ -38,7 +38,7 @@ mindplot.commands.ChangeNoteToTopicCommand = new Class({
     },
 
     undoExecute: function(commandContext) {
-        var topic = commandContext.findTopics(this._objectsIds)[0];
+        var topic = commandContext.findTopics(this._topicsIds)[0];
         if (this._oldtext) {
             topic.removeNote();
             topic.addNote(this._oldtext);
diff --git a/mindplot/src/main/javascript/commands/DeleteCommand.js b/mindplot/src/main/javascript/commands/DeleteCommand.js
index f6af98ec..650168f6 100644
--- a/mindplot/src/main/javascript/commands/DeleteCommand.js
+++ b/mindplot/src/main/javascript/commands/DeleteCommand.js
@@ -19,6 +19,8 @@
 mindplot.commands.DeleteCommand = new Class({
     Extends:mindplot.Command,
     initialize: function(topicIds, relIds) {
+        $assert($defined(topicIds), 'topicIds can not be null');
+
         this._relIds = relIds;
         this._topicIds = topicIds;
         this._deletedTopicModels = [];
diff --git a/mindplot/src/main/javascript/commands/DragTopicCommand.js b/mindplot/src/main/javascript/commands/DragTopicCommand.js
index e8aee711..95fde129 100644
--- a/mindplot/src/main/javascript/commands/DragTopicCommand.js
+++ b/mindplot/src/main/javascript/commands/DragTopicCommand.js
@@ -21,7 +21,7 @@ mindplot.commands.DragTopicCommand = new Class({
     initialize: function(topicIds, position, order, parentTopic) {
         $assert(topicIds, "topicIds must be defined");
 
-        this._objectsIds = topicIds;
+        this._topicsIds = topicIds;
         if ($defined(parentTopic))
             this._parentId = parentTopic.getId();
 
@@ -32,7 +32,7 @@ mindplot.commands.DragTopicCommand = new Class({
 
     execute: function(commandContext) {
 
-        var topic = commandContext.findTopics([this._objectsIds])[0];
+        var topic = commandContext.findTopics([this._topicsIds])[0];
 
         // Save old position ...
         var origParentTopic = topic.getOutgoingConnectedTopic();
diff --git a/mindplot/src/main/javascript/commands/GenericFunctionCommand.js b/mindplot/src/main/javascript/commands/GenericFunctionCommand.js
index 0dc6f896..b2552103 100644
--- a/mindplot/src/main/javascript/commands/GenericFunctionCommand.js
+++ b/mindplot/src/main/javascript/commands/GenericFunctionCommand.js
@@ -23,14 +23,14 @@ mindplot.commands.GenericFunctionCommand = new Class({
         $assert(topicsIds, "topicsIds must be defined");
 
         this._value = value;
-        this._objectsIds = topicsIds;
+        this._topicsIds = topicsIds;
         this._commandFunc = commandFunc;
         this._oldValues = [];
         this._id = mindplot.Command._nextUUID();
     },
     execute: function(commandContext) {
         if (!this.applied) {
-            var topics = commandContext.findTopics(this._objectsIds);
+            var topics = commandContext.findTopics(this._topicsIds);
             topics.forEach(function(topic) {
                 var oldValue = this._commandFunc(topic, this._value);
                 this._oldValues.push(oldValue);
@@ -43,7 +43,7 @@ mindplot.commands.GenericFunctionCommand = new Class({
     },
     undoExecute: function(commandContext) {
         if (this.applied) {
-            var topics = commandContext.findTopics(this._objectsIds);
+            var topics = commandContext.findTopics(this._topicsIds);
             topics.forEach(function(topic, index) {
                 this._commandFunc(topic, this._oldValues[index]);
 
diff --git a/mindplot/src/main/javascript/commands/RemoveIconFromTopicCommand.js b/mindplot/src/main/javascript/commands/RemoveIconFromTopicCommand.js
index 03cd05e5..32717760 100644
--- a/mindplot/src/main/javascript/commands/RemoveIconFromTopicCommand.js
+++ b/mindplot/src/main/javascript/commands/RemoveIconFromTopicCommand.js
@@ -19,19 +19,19 @@
 mindplot.commands.RemoveIconFromTopicCommand = new Class({
     Extends:mindplot.Command,
     initialize: function(topicIds, iconModel) {
-        $assert(topicIds, 'topicIds can not be null');
+        $assert($defined(topicIds), 'topicIds can not be null');
         $assert(iconModel, 'iconModel can not be null');
-        this._objectsIds = topicIds;
+        this._topicsIds = topicIds;
         this._iconModel = iconModel;
     },
 
     execute: function(commandContext) {
-        var topic = commandContext.findTopics(this._objectsIds)[0];
+        var topic = commandContext.findTopics(this._topicsIds)[0];
         topic.removeIcon(this._iconModel);
     },
 
     undoExecute: function(commandContext) {
-        var topic = commandContext.findTopics(this._objectsIds)[0];
+        var topic = commandContext.findTopics(this._topicsIds)[0];
         var iconType = this._iconModel.getIconType();
         var iconImg = topic.addIcon(iconType, commandContext._designer);
         this._iconModel = iconImg.getModel();
diff --git a/mindplot/src/main/javascript/commands/RemoveLinkFromTopicCommand.js b/mindplot/src/main/javascript/commands/RemoveLinkFromTopicCommand.js
index bb759485..3800c91b 100644
--- a/mindplot/src/main/javascript/commands/RemoveLinkFromTopicCommand.js
+++ b/mindplot/src/main/javascript/commands/RemoveLinkFromTopicCommand.js
@@ -19,12 +19,12 @@
 mindplot.commands.RemoveLinkFromTopicCommand = new Class({
     Extends:mindplot.Command,
     initialize: function(topicId) {
-        $assert(topicId, 'topicId can not be null');
-        this._objectsIds = topicId;
+        $assert($defined(topicId), 'topicId can not be null');
+        this._topicsIds = topicId;
     },
 
     execute: function(commandContext) {
-        var topic = commandContext.findTopics(this._objectsIds)[0];
+        var topic = commandContext.findTopics(this._topicsIds)[0];
         var model = topic.getModel();
         var links = model.getLinks()[0];
         this._text = links.getUrl();
@@ -32,7 +32,7 @@ mindplot.commands.RemoveLinkFromTopicCommand = new Class({
     },
 
     undoExecute: function(commandContext) {
-        var topic = commandContext.findTopics(this._objectsIds)[0];
+        var topic = commandContext.findTopics(this._topicsIds)[0];
         topic.addLink(this._url, commandContext._designer);
     }
 });
\ No newline at end of file
diff --git a/mindplot/src/main/javascript/commands/RemoveNoteFromTopicCommand.js b/mindplot/src/main/javascript/commands/RemoveNoteFromTopicCommand.js
index 7c042845..230e191d 100644
--- a/mindplot/src/main/javascript/commands/RemoveNoteFromTopicCommand.js
+++ b/mindplot/src/main/javascript/commands/RemoveNoteFromTopicCommand.js
@@ -19,18 +19,18 @@
 mindplot.commands.RemoveNoteFromTopicCommand = new Class({
     Extends:mindplot.Command,
     initialize: function(topicId) {
-        $assert(topicId, 'topicId can not be null');
-        this._objectsIds = topicId;
+        $assert($defined(topicId), 'topicId can not be null');
+        this._topicsIds = topicId;
     },
     execute: function(commandContext) {
-        var topic = commandContext.findTopics(this._objectsIds)[0];
+        var topic = commandContext.findTopics(this._topicsIds)[0];
         var model = topic.getModel();
         var notes = model.getNotes()[0];
         this._text = notes.getText();
         topic.removeNote();
     },
     undoExecute: function(commandContext) {
-        var topic = commandContext.findTopics(this._objectsIds)[0];
+        var topic = commandContext.findTopics(this._topicsIds)[0];
         topic.addNote(this._text, commandContext._designer);
     }
 });
\ No newline at end of file