Index: b/modeshape-jcr/src/main/java/org/modeshape/jcr/JcrNodeDefinition.java
===================================================================
--- a/modeshape-jcr/src/main/java/org/modeshape/jcr/JcrNodeDefinition.java	(revision )
+++ b/modeshape-jcr/src/main/java/org/modeshape/jcr/JcrNodeDefinition.java	(working copy)
@@ -173,6 +173,13 @@ class JcrNodeDefinition extends JcrItemDefinition implements NodeDefinition {
      */
     public NodeType[] getRequiredPrimaryTypes() {
         ensureRequiredPrimaryTypesLoaded();
+        if (requiredPrimaryTypes.length == 0) {
+            // Per the JavaDoc, this method should never return null or an empty array; if there are no constraints,
+            // then this method should include an array with 'nt:base' as the required primary type.
+            NodeType[] result = new NodeType[1];
+            result[0] = nodeTypeManager.getNodeType(JcrNtLexicon.BASE);
+            return result;
+        }
         // Make a copy so that the caller can't modify our content ...
         NodeType[] result = new NodeType[requiredPrimaryTypes.length];
         for (int i = 0; i != requiredPrimaryTypes.length; ++i) {
Index: b/modeshape-jcr/src/main/java/org/modeshape/jcr/JcrNodeDefinitionTemplate.java
===================================================================
--- a/modeshape-jcr/src/main/java/org/modeshape/jcr/JcrNodeDefinitionTemplate.java	(revision )
+++ b/modeshape-jcr/src/main/java/org/modeshape/jcr/JcrNodeDefinitionTemplate.java	(working copy)
@@ -49,6 +49,9 @@ class JcrNodeDefinitionTemplate extends JcrItemDefinitionTemplate implements Nod
 
     /**
      * {@inheritDoc}
+     * <p>
+     * Passing a null or blank name is equivalent to "unsetting" (or removing) the primary item name.
+     * </p>
      * 
      * @see org.modeshape.jcr.nodetype.NodeDefinitionTemplate#setDefaultPrimaryType(String)
      */
@@ -59,14 +62,18 @@ class JcrNodeDefinitionTemplate extends JcrItemDefinitionTemplate implements Nod
     /**
      * Set the name of the primary type that should be used by default when creating children using this node definition
      * 
-     * @param defaultPrimaryType the default primary type for this child node
+     * @param defaultPrimaryType the default primary type for this child node, or null if there is to be no default primary type
      * @throws ConstraintViolationException
      */
     public void setDefaultPrimaryTypeName( String defaultPrimaryType ) throws ConstraintViolationException {
-        try {
-            this.defaultPrimaryType = getContext().getValueFactories().getNameFactory().create(defaultPrimaryType);
-        } catch (ValueFormatException vfe) {
-            throw new ConstraintViolationException(vfe);
+        if (defaultPrimaryType == null || defaultPrimaryType.trim().length() == 0) {
+            this.defaultPrimaryType = null;
+        } else {
+            try {
+                this.defaultPrimaryType = getContext().getValueFactories().getNameFactory().create(defaultPrimaryType);
+            } catch (ValueFormatException vfe) {
+                throw new ConstraintViolationException(vfe);
+            }
         }
     }
 
@@ -142,9 +149,15 @@ class JcrNodeDefinitionTemplate extends JcrItemDefinitionTemplate implements Nod
      * @see javax.jcr.nodetype.NodeDefinition#getRequiredPrimaryTypes()
      */
     public NodeType[] getRequiredPrimaryTypes() {
+        // This method should return null since it's not attached to a registered node type ...
         return null;
     }
 
+    /**
+     * {@inheritDoc}
+     * 
+     * @see javax.jcr.nodetype.NodeDefinition#getRequiredPrimaryTypeNames()
+     */
     public String[] getRequiredPrimaryTypeNames() {
         if (requiredPrimaryTypes == null) return null;
 
Index: b/modeshape-jcr/src/main/java/org/modeshape/jcr/JcrNodeTypeTemplate.java
===================================================================
--- a/modeshape-jcr/src/main/java/org/modeshape/jcr/JcrNodeTypeTemplate.java	(revision )
+++ b/modeshape-jcr/src/main/java/org/modeshape/jcr/JcrNodeTypeTemplate.java	(working copy)
@@ -166,15 +166,22 @@ public class JcrNodeTypeTemplate implements NodeTypeDefinition, NodeTypeTemplate
 
     /**
      * {@inheritDoc}
+     * <p>
+     * Passing a null or blank name is equivalent to "unsetting" (or removing) the primary item name.
+     * </p>
      * 
      * @see org.modeshape.jcr.nodetype.NodeTypeDefinition#getPrimaryItemName()
      *      type.NodeTypeTemplate#setPrimaryItemName(java.lang.String)
      */
     public void setPrimaryItemName( String name ) throws ConstraintViolationException {
-        try {
-            this.primaryItemName = context.getValueFactories().getNameFactory().create(name);
-        } catch (ValueFormatException vfe) {
-            throw new ConstraintViolationException(vfe);
+        if (name == null || name.trim().length() == 0) {
+            this.primaryItemName = null;
+        } else {
+            try {
+                this.primaryItemName = context.getValueFactories().getNameFactory().create(name);
+            } catch (ValueFormatException vfe) {
+                throw new ConstraintViolationException(vfe);
+            }
         }
     }
 
Index: b/modeshape-jcr/src/main/java/org/modeshape/jcr/JcrPropertyDefinitionTemplate.java
===================================================================
--- a/modeshape-jcr/src/main/java/org/modeshape/jcr/JcrPropertyDefinitionTemplate.java	(revision )
+++ b/modeshape-jcr/src/main/java/org/modeshape/jcr/JcrPropertyDefinitionTemplate.java	(working copy)
@@ -52,15 +52,14 @@ class JcrPropertyDefinitionTemplate extends JcrItemDefinitionTemplate implements
      * @see org.modeshape.jcr.nodetype.PropertyDefinitionTemplate#setDefaultValues(java.lang.String[])
      */
     public void setDefaultValues( String[] defaultValues ) {
-        if (defaultValues == null) {
+        if (defaultValues != null) {
+            this.defaultValues = new Value[defaultValues.length];
+            ValueFactories factories = getExecutionContext().getValueFactories();
+            for (int i = 0; i < defaultValues.length; i++) {
+                this.defaultValues[i] = new JcrValue(factories, null, PropertyType.STRING, defaultValues[i]);
+            }
+        } else {
             this.defaultValues = null;
-            return;
-        }
-
-        this.defaultValues = new Value[defaultValues.length];
-        ValueFactories factories = getExecutionContext().getValueFactories();
-        for (int i = 0; i < defaultValues.length; i++) {
-            this.defaultValues[i] = new JcrValue(factories, null, PropertyType.STRING, defaultValues[i]);
         }
     }
 
@@ -92,8 +91,8 @@ class JcrPropertyDefinitionTemplate extends JcrItemDefinitionTemplate implements
                || requiredType == PropertyType.DOUBLE || requiredType == PropertyType.DECIMAL
                || requiredType == PropertyType.LONG || requiredType == PropertyType.NAME || requiredType == PropertyType.PATH
                || requiredType == PropertyType.REFERENCE || requiredType == PropertyType.WEAKREFERENCE
-               || requiredType == PropertyType.URI
-               || requiredType == PropertyType.STRING || requiredType == PropertyType.UNDEFINED;
+               || requiredType == PropertyType.URI || requiredType == PropertyType.STRING
+               || requiredType == PropertyType.UNDEFINED;
         this.requiredType = requiredType;
     }