diff --git a/org.fortiss.af3.state.ui/src/org/fortiss/af3/state/ui/editor/fx/.ratings b/org.fortiss.af3.state.ui/src/org/fortiss/af3/state/ui/editor/fx/.ratings
index c37405b77efc4c92f0c772c370ab137b844e612c..7bbf50b1189b3280e81d4ef6e2e7e62cd7deb20c 100644
--- a/org.fortiss.af3.state.ui/src/org/fortiss/af3/state/ui/editor/fx/.ratings
+++ b/org.fortiss.af3.state.ui/src/org/fortiss/af3/state/ui/editor/fx/.ratings
@@ -1,5 +1,5 @@
 DataStateFXEditor.java e64fcec84ea83e5ba99e48a6825063471e9ea70d GREEN
-DataStateFXEditorBase.java 0bec3533962ebcd7326f6597d598a5ff7c8ba8e6 GREEN
+DataStateFXEditorBase.java 83655742fdcfdade31eabd7deafa88862f28ba22 GREEN
 DataStateFXEditorBinding.java 46ab36b197a6fca102a5e2d75aa24b1fbba26b89 GREEN
 DataStateFXEditorContentProvider.java 324cd24e2219ba2cf360b0f82e3628ca1b5dabba GREEN
 DataStateFXEditorUIProvider.java 4993d4a6685b7738dd28a7a55177ab43fe81fc53 GREEN
diff --git a/org.fortiss.af3.state.ui/src/org/fortiss/af3/state/ui/editor/fx/DataStateFXEditorBase.java b/org.fortiss.af3.state.ui/src/org/fortiss/af3/state/ui/editor/fx/DataStateFXEditorBase.java
index 0bec3533962ebcd7326f6597d598a5ff7c8ba8e6..83655742fdcfdade31eabd7deafa88862f28ba22 100644
--- a/org.fortiss.af3.state.ui/src/org/fortiss/af3/state/ui/editor/fx/DataStateFXEditorBase.java
+++ b/org.fortiss.af3.state.ui/src/org/fortiss/af3/state/ui/editor/fx/DataStateFXEditorBase.java
@@ -19,17 +19,21 @@ import static org.eclipse.emf.ecore.util.EcoreUtil.delete;
 import static org.fortiss.af3.component.utils.BehaviorModelElementFactory.createDataStateVariable;
 import static org.fortiss.af3.expression.utils.ExpressionModelElementFactory.intConst;
 import static org.fortiss.af3.expression.utils.ExpressionModelElementFactory.intType;
+import static org.fortiss.tooling.common.ui.javafx.util.GraphicUtils.getFXImage;
 
 import java.util.List;
 
+import org.eclipse.core.runtime.IStatus;
 import org.eclipse.emf.common.notify.Notification;
 import org.eclipse.emf.ecore.EObject;
 import org.fortiss.af3.component.model.behavior.common.DataStateVariable;
 import org.fortiss.af3.component.model.behavior.common.IDataStateVariableProvider;
+import org.fortiss.af3.expression.ui.databinding.validate.StringToTypeValidator;
 import org.fortiss.tooling.common.ui.javafx.control.treetableview.DynamicTreeContentProviderBase;
 import org.fortiss.tooling.common.ui.javafx.control.treetableview.DynamicTreeTableViewer;
 import org.fortiss.tooling.kernel.extension.data.ITopLevelElement;
 import org.fortiss.tooling.kernel.service.IPersistencyService;
+import org.fortiss.tooling.kernel.ui.ToolingKernelUIActivator;
 import org.fortiss.tooling.kernel.ui.extension.base.FXEditorBase;
 import org.fortiss.tooling.kernel.utils.KernelServiceBasedModelListenerBase;
 
@@ -37,6 +41,10 @@ import javafx.event.ActionEvent;
 import javafx.event.EventHandler;
 import javafx.scene.Parent;
 import javafx.scene.control.Button;
+import javafx.scene.control.Label;
+import javafx.scene.image.ImageView;
+import javafx.scene.input.KeyCode;
+import javafx.scene.input.KeyEvent;
 import javafx.scene.layout.BorderPane;
 import javafx.scene.layout.VBox;
 
@@ -47,18 +55,18 @@ import javafx.scene.layout.VBox;
  */
 public abstract class DataStateFXEditorBase<T extends IDataStateVariableProvider>
 		extends FXEditorBase<T> {
-
+	/** The description. */
+	private static final String DESCRIPTION = "Define data state variables with the table below:";
 	/** The tree-table viewer. */
 	private DynamicTreeTableViewer<EObject> viewer;
-
 	/** The remove button. */
 	private Button removeButton;
-
 	/** The add button. */
 	private Button addButton;
-
 	/** The model listener. */
 	private KernelServiceBasedModelListenerBase<IDataStateVariableProvider> modelListener;
+	/** The description / error label. */
+	private Label descriptionError;
 
 	/** {@inheritDoc} */
 	@Override
@@ -76,10 +84,39 @@ public abstract class DataStateFXEditorBase<T extends IDataStateVariableProvider
 
 		DynamicTreeContentProviderBase<EObject> contentProvider =
 				new DataStateFXEditorContentProvider();
-		DataStateFXEditorUIProvider uiProvider = new DataStateFXEditorUIProvider();
+		DataStateFXEditorUIProvider uiProvider = new DataStateFXEditorUIProvider() {
+			@Override
+			public void validateOnKeyReleased(KeyEvent event, int colIndex, EObject item,
+					String text) {
+				String message = DataStateFXEditorBase.DESCRIPTION;
+				ImageView icon = null;
+				if(event.getCode() != KeyCode.ESCAPE && colIndex == 1) {
+					StringToTypeValidator validator = new StringToTypeValidator(item);
+					IStatus status = validator.validate(text);
+					if(!status.isOK()) {
+						message = status.getMessage();
+						icon = new ImageView(
+								getFXImage(ToolingKernelUIActivator.PLUGIN_ID, "/icons/error.png"));
+					}
+				}
+				descriptionError.setText(message);
+				descriptionError.setGraphic(icon);
+				event.consume();
+			}
+
+			/** {@inheritDoc} */
+			@Override
+			public void validateOnCancelEdit(int colIndex, EObject item) {
+				descriptionError.setText(DataStateFXEditorBase.DESCRIPTION);
+				descriptionError.setGraphic(null);
+			}
+		};
 
 		// Add main pane with the table.
 		BorderPane mainPane = new BorderPane();
+		descriptionError = new Label(DESCRIPTION);
+		mainPane.setTop(descriptionError);
+
 		viewer = new DynamicTreeTableViewer<>(provider, false, 2, contentProvider, uiProvider);
 		viewer.addColumn("Variable", 160);
 		viewer.addColumn("Type", 160);