Index: editor/repository/src/main/resources/cms-validators.xml
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>UTF-8
===================================================================
--- editor/repository/src/main/resources/cms-validators.xml	(revision 34367)
+++ editor/repository/src/main/resources/cms-validators.xml	(revision )
@@ -67,6 +67,17 @@
       <sv:value>^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,6}$</sv:value>
     </sv:property>
   </sv:node>
+  <sv:node sv:name="references">
+    <sv:property sv:name="jcr:primaryType" sv:type="Name">
+      <sv:value>frontend:plugin</sv:value>
+    </sv:property>
+    <sv:property sv:name="plugin.class" sv:type="String">
+      <sv:value>org.hippoecm.frontend.editor.validator.plugins.NodeReferenceValidator</sv:value>
+    </sv:property>
+    <sv:property sv:name="translator.id" sv:type="String">
+      <sv:value>validation.service.translator.config</sv:value>
+    </sv:property>
+  </sv:node>
   <sv:node sv:name="validationTranslator">
     <sv:property sv:name="jcr:primaryType" sv:type="Name">
       <sv:value>frontend:plugin</sv:value>
\ No newline at end of file
Index: editor/frontend/src/main/java/org/hippoecm/frontend/editor/validator/plugins/NodeReferenceValidator.java
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>UTF-8
===================================================================
--- editor/frontend/src/main/java/org/hippoecm/frontend/editor/validator/plugins/NodeReferenceValidator.java	(revision )
+++ editor/frontend/src/main/java/org/hippoecm/frontend/editor/validator/plugins/NodeReferenceValidator.java	(revision )
@@ -0,0 +1,52 @@
+/*
+ * Copyright 2012 Hippo.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *         http://www.apache.org/licenses/LICENSE-2.
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.hippoecm.frontend.editor.validator.plugins;
+
+import java.util.HashSet;
+import java.util.Set;
+
+import org.apache.wicket.model.IModel;
+import org.hippoecm.frontend.model.JcrNodeModel;
+import org.hippoecm.frontend.plugin.IPluginContext;
+import org.hippoecm.frontend.plugin.config.IPluginConfig;
+import org.hippoecm.frontend.validation.IFieldValidator;
+import org.hippoecm.frontend.validation.ValidationException;
+import org.hippoecm.frontend.validation.Violation;
+
+public class NodeReferenceValidator extends AbstractCmsValidator {
+
+    public NodeReferenceValidator(IPluginContext context, IPluginConfig config) {
+        super(context, config);
+    }
+
+    @Override
+    public void preValidation(final IFieldValidator type) throws ValidationException {
+        if (!"String".equals(type.getFieldType().getType())) {
+            throw new ValidationException("Invalid validation exception; cannot validate non-string field for emptiness");
+        }
+    }
+
+    @Override
+    public Set<Violation> validate(final IFieldValidator fieldValidator, final JcrNodeModel model, final IModel childModel) throws ValidationException {
+        Set<Violation> violations = new HashSet<Violation>();
+        String ref = (String) childModel.getObject();
+        if(ref == null || ref.equals("") || ref.equals("cafebabe-cafe-babe-cafe-babecafebabe")) {
+            violations.add(fieldValidator.newValueViolation(childModel, "reference-is-empty"));
+        }
+        return violations;
+    }
+}
Index: editor/frontend/src/main/java/org/hippoecm/frontend/editor/validator/ValidationFeedback.properties
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>MacRoman
===================================================================
--- editor/frontend/src/main/java/org/hippoecm/frontend/editor/validator/ValidationFeedback.properties	(revision 34367)
+++ editor/frontend/src/main/java/org/hippoecm/frontend/editor/validator/ValidationFeedback.properties	(revision )
@@ -4,3 +4,4 @@
 invalid-character=Invalid character present
 invalid-xml=XML is not valid
 html-is-empty=Rich text field is empty
+reference-is-empty=Reference is empty
\ No newline at end of file
Index: editor/repository/src/main/resources/namespace-hippo.xml
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>UTF-8
===================================================================
--- editor/repository/src/main/resources/namespace-hippo.xml	(revision 34367)
+++ editor/repository/src/main/resources/namespace-hippo.xml	(revision )
@@ -545,6 +545,9 @@
           <sv:property sv:name="hipposysedit:type" sv:type="String">
             <sv:value>Docbase</sv:value>
           </sv:property>
+          <sv:property sv:name="hipposysedit:validators" sv:type="String" sv:multiple="true">
+            <sv:value>references</sv:value>
+          </sv:property>
         </sv:node>
         <sv:node sv:name="tree">
           <sv:property sv:name="jcr:primaryType" sv:type="Name">