diff --git a/platform/commonUI/general/bundle.json b/platform/commonUI/general/bundle.json
index 4c3bbd0a2b..2bf8f37c47 100644
--- a/platform/commonUI/general/bundle.json
+++ b/platform/commonUI/general/bundle.json
@@ -29,8 +29,8 @@
                 "depends": [ "$scope" ]
             },
             {
-                "key": "AccordionController",
-                "implementation": "AccordionController.js"
+                "key": "ToggleController",
+                "implementation": "ToggleController.js"
             },
             {
                 "key": "ContextMenuController",
diff --git a/platform/commonUI/general/res/templates/containers/accordion.html b/platform/commonUI/general/res/templates/containers/accordion.html
index f549fa13b4..c39719f77d 100644
--- a/platform/commonUI/general/res/templates/containers/accordion.html
+++ b/platform/commonUI/general/res/templates/containers/accordion.html
@@ -1,9 +1,9 @@
-<div class="accordion" ng-controller="AccordionController as accordion">
-    <div class="accordion-head" ng-click="accordion.toggle()">
+<div class="accordion" ng-controller="ToggleController as toggle">
+    <div class="accordion-head" ng-click="toggle.toggle()">
         {{container.title}}
     </div>
     <div class="accordion-contents"
-         ng-show="accordion.expanded()"
+         ng-show="toggle.isActive()"
          style="height: 180px;"
          ng-transclude>
     </div>
diff --git a/platform/commonUI/general/res/templates/tree-item.html b/platform/commonUI/general/res/templates/tree-item.html
index 757957e996..60c3ed276a 100644
--- a/platform/commonUI/general/res/templates/tree-item.html
+++ b/platform/commonUI/general/res/templates/tree-item.html
@@ -1,7 +1,9 @@
-<span ng-controller="TreeNodeController">
-<span class="tree-item menus-to-left">
-	<span class='ui-symbol view-control' ng-click="toggle()" ng-if="model.composition !== undefined">
-        {{node.expanded ? "v" : ">"}}
+<span ng-controller="ToggleController as toggle">
+<span class="tree-item menus-to-left" ng-controller="TreeNodeController">
+	<span class='ui-symbol view-control'
+          ng-click="toggle.toggle()"
+          ng-if="model.composition !== undefined">
+        {{toggle.isActive() ? "v" : ">"}}
     </span>
     <mct-representation key="'label'"
                         mct-object="domainObject"
@@ -10,7 +12,9 @@
                         ng-class="{selected: node.isSelected}">
     </mct-representation>
 </span>
-<span class="tree-item-subtree" ng-show="node.expanded" ng-if="model.composition !== undefined">
+<span class="tree-item-subtree"
+      ng-show="toggle.isActive()"
+      ng-if="model.composition !== undefined">
     <mct-representation key="'tree'"
                         parameters="parameters"
                         mct-object="node.domainObject">
diff --git a/platform/commonUI/general/src/AccordionController.js b/platform/commonUI/general/src/AccordionController.js
deleted file mode 100644
index 56e2e74d23..0000000000
--- a/platform/commonUI/general/src/AccordionController.js
+++ /dev/null
@@ -1,29 +0,0 @@
-/*global define,Promise*/
-
-/**
- * Module defining AccordionController. Created by vwoeltje on 11/14/14.
- */
-define(
-    [],
-    function () {
-        "use strict";
-
-        /**
-         *
-         * @constructor
-         */
-        function AccordionController() {
-            var isExpanded = true;
-            return {
-                toggle: function () {
-                    isExpanded = !isExpanded;
-                },
-                expanded: function () {
-                    return isExpanded;
-                }
-            };
-        }
-
-        return AccordionController;
-    }
-);
\ No newline at end of file
diff --git a/platform/commonUI/general/src/ActionGroupController.js b/platform/commonUI/general/src/ActionGroupController.js
index b9fb3e8d42..5f1c2d3ea1 100644
--- a/platform/commonUI/general/src/ActionGroupController.js
+++ b/platform/commonUI/general/src/ActionGroupController.js
@@ -38,7 +38,7 @@ define(
 
             function updateGroups() {
                 var actionCapability = $scope.action,
-                    params = $scope.parameters ? $scope.parameters : {},
+                    params = $scope.parameters || {},
                     category = params.category;
 
                 if (actionCapability && category) {
diff --git a/platform/commonUI/general/src/ToggleController.js b/platform/commonUI/general/src/ToggleController.js
new file mode 100644
index 0000000000..e1268a47bb
--- /dev/null
+++ b/platform/commonUI/general/src/ToggleController.js
@@ -0,0 +1,45 @@
+/*global define,Promise*/
+
+define(
+    [],
+    function () {
+        "use strict";
+
+        /**
+         * A ToggleController is used to activate/deactivate things.
+         * A common usage is for "twistie"
+         *
+         * @constructor
+         */
+        function ToggleController() {
+            var state = false;
+
+            return {
+                /**
+                 * Get the current state of the toggle.
+                 * @return {boolean} true if active
+                 */
+                isActive: function () {
+                    return state;
+                },
+                /**
+                 * Set a new state for the toggle.
+                 * @return {boolean} true to activate
+                 */
+                setState: function (newState) {
+                    state = newState;
+                },
+                /**
+                 * Toggle the current state; activate if it is inactive,
+                 * deactivate if it is active.
+                 */
+                toggle: function () {
+                    state = !state;
+                }
+            };
+
+        }
+
+        return ToggleController;
+    }
+);
\ No newline at end of file
diff --git a/platform/commonUI/general/src/TreeNodeController.js b/platform/commonUI/general/src/TreeNodeController.js
index 64b9e8677b..1593393fe7 100644
--- a/platform/commonUI/general/src/TreeNodeController.js
+++ b/platform/commonUI/general/src/TreeNodeController.js
@@ -29,6 +29,15 @@ define(
                 return obj.getId();
             }
 
+            // Verify that id paths are equivalent, staring at
+            // index, ending at the end of the node path.
+            function checkPath(nodePath, navPath, index) {
+                index = index || 0;
+                return index > nodePath.length ||
+                        (navPath[index] === nodePath[index] &&
+                                checkPath(nodePath, navPath, index + 1));
+            }
+
             function isOnNavigationPath(nodeObject, navObject) {
                 var nodeContext = nodeObject &&
                             nodeObject.getCapability('context'),
@@ -41,12 +50,7 @@ define(
                     nodePath = nodeContext.getPath().map(getId);
                     navPath = navContext.getPath().map(getId);
                     return (navPath.length > nodePath.length) &&
-                            nodePath.map(function (id, i) {
-                                return id === navPath[i];
-                            }).reduce(function (a, b) {
-                                return a && b;
-                            }, true);
-
+                            checkPath(nodePath, navPath);
                 }
                 return false; // No context to judge by
             }
@@ -58,8 +62,10 @@ define(
                     idsEqual(nodeObject, navigatedObject) &&
                             idsEqual(parentOf(nodeObject), parentOf(navigatedObject));
                 // Expand if necessary
-                if (!$scope.node.expanded && isOnNavigationPath(nodeObject, navigatedObject)) {
-                    $scope.toggle();
+                if (!$scope.node.expanded &&
+                        isOnNavigationPath(nodeObject, navigatedObject) &&
+                        $scope.toggle !== undefined) {
+                    $scope.toggle.toggle();
                 }
             }
 
@@ -68,21 +74,25 @@ define(
                 checkNavigation();
             }
 
-            $scope.node = { expanded: false };
+            // When the node is expanded, set "node.domainObject" in
+            // the scope; this is used to populate the subtree, which
+            // should only happen when first expanded (lazy loading)
+            function doExpand(state) {
+                if (state) {
+                    $scope.node.domainObject = $scope.domainObject;
+                }
+            }
 
-            $scope.toggle = function () {
-                var expanded = !$scope.node.expanded;
-                $scope.node.expanded = expanded;
-
-                // Trigger load of composition, if needed
-                $scope.node.domainObject = $scope.domainObject;
-            };
+            // Set up a little namespace for tree node properties
+            $scope.node = {};
 
             navigationService.addListener(setNavigation);
             $scope.$on("$destroy", function () {
                 navigationService.removeListener(setNavigation);
             });
             $scope.$watch("domainObject", checkNavigation);
+            $scope.$watch("toggle.isActive()", doExpand);
+
         }
 
         return TreeNodeController;