reversing that expiriment, not surprisingly it didn't work
diff --git a/jpa/plugins/org.eclipse.jpt.core/plugin.xml b/jpa/plugins/org.eclipse.jpt.core/plugin.xml
index 2b4dfba..0894b9d 100644
--- a/jpa/plugins/org.eclipse.jpt.core/plugin.xml
+++ b/jpa/plugins/org.eclipse.jpt.core/plugin.xml
@@ -15,7 +15,7 @@
 	<!-- ***** Eclipse core extensions ***** -->
 	
 	<extension
-		point="org.eclipse.core.contenttype.contentTypes">
+		point="org.eclipse.core.runtime.contentTypes">
 		
 		<!-- "abstract" content type to be extended by all JPA XML file content types -->
 		<content-type
@@ -25,11 +25,18 @@
 			describer="org.eclipse.jpt.core.internal.resource.IndeterminateContentDescriber">
 		</content-type>
 		
+		<!-- "abstract" persistence file content type -->
+		<content-type
+			id="org.eclipse.jpt.core.content.persistenceFile"
+			name="%PERSISTENCE_FILE_CONTENT"
+			base-type="org.eclipse.jpt.core.content.baseJpaContent">
+		</content-type>
+		
 		<!-- persistence.xml version 1.0 content type -->
   		<content-type
 			id="org.eclipse.jpt.core.content.persistence"
 			name="%PERSISTENCE_XML_CONTENT"
-			base-type="org.eclipse.jpt.core.content.baseJpaContent"
+			base-type="org.eclipse.jpt.core.content.persistenceFile"
 			file-names="persistence.xml">
 			<describer
 				class="org.eclipse.jpt.core.internal.resource.xml.XMLRootElementVersionContentDescriber">
@@ -43,7 +50,7 @@
   		<content-type
 			id="org.eclipse.jpt.core.content.persistence2_0"
 			name="%PERSISTENCE2_0_XML_CONTENT"
-			base-type="org.eclipse.jpt.core.content.persistence"
+			base-type="org.eclipse.jpt.core.content.persistenceFile"
 			file-names="persistence.xml">
 			<describer
 				class="org.eclipse.jpt.core.internal.resource.xml.XMLRootElementVersionContentDescriber">
@@ -54,11 +61,18 @@
 			</describer>
 		</content-type>
 		
+		<!-- "abstract" mapping file content type -->
+		<content-type
+			id="org.eclipse.jpt.core.content.mappingFile"
+			name="%MAPPING_FILE_CONTENT"
+			base-type="org.eclipse.jpt.core.content.baseJpaContent">
+		</content-type>
+		
 		<!-- orm.xml version 1.0 content type -->
 		<content-type
 			id="org.eclipse.jpt.core.content.orm"
 			name="%ORM_XML_CONTENT"
-			base-type="org.eclipse.jpt.core.content.baseJpaContent">
+			base-type="org.eclipse.jpt.core.content.mappingFile">
 			<describer
 				class="org.eclipse.jpt.core.internal.resource.xml.XMLRootElementVersionContentDescriber">
 				<parameter 
@@ -69,9 +83,9 @@
 		
 		<!-- orm.xml version 2.0 content type -->
 		<content-type
+			base-type="org.eclipse.jpt.core.content.mappingFile"
 	        id="org.eclipse.jpt.core.content.orm2_0"
-	        name="%ORM2_0_XML_CONTENT"
-			base-type="org.eclipse.jpt.core.content.orm">
+	        name="%ORM2_0_XML_CONTENT">
 	     	<describer
 	           class="org.eclipse.jpt.core.internal.resource.xml.XMLRootElementVersionContentDescriber">
 	        	<parameter
diff --git a/jpa/plugins/org.eclipse.jpt.core/src/org/eclipse/jpt/core/JptCorePlugin.java b/jpa/plugins/org.eclipse.jpt.core/src/org/eclipse/jpt/core/JptCorePlugin.java
index fd1a9fd..35dcddf 100644
--- a/jpa/plugins/org.eclipse.jpt.core/src/org/eclipse/jpt/core/JptCorePlugin.java
+++ b/jpa/plugins/org.eclipse.jpt.core/src/org/eclipse/jpt/core/JptCorePlugin.java
@@ -114,6 +114,11 @@
 	 * The content type for Java source code files.
 	 */
 	public static final IContentType JAVA_SOURCE_CONTENT_TYPE = getContentType(JavaCore.JAVA_SOURCE_CONTENT_TYPE);
+
+	/**
+	 * The base content type for all persistence.xml files.
+	 */
+	public static final IContentType PERSISTENCE_FILE_CONTENT_TYPE = getJpaContentType("persistenceFile"); //$NON-NLS-1$
 	
 	/**
 	 * The content type for persistence.xml 1.0 (based on the persistence 1.0 schema) files.
@@ -124,7 +129,12 @@
 	 * The content type for persistence.xml 2.0 (based on the persistence 2.0 schema) files.
 	 */
 	public static final IContentType PERSISTENCE2_0_XML_CONTENT_TYPE = getJpaContentType("persistence2_0"); //$NON-NLS-1$
-		
+	
+	/**
+	 * The base content type for all mapping files.
+	 */
+	public static final IContentType MAPPING_FILE_CONTENT_TYPE = getJpaContentType("mappingFile"); //$NON-NLS-1$
+	
 	/**
 	 * The content type for orm.xml 1.0 (based on the orm 1.0 schema) mapping files.
 	 */
diff --git a/jpa/plugins/org.eclipse.jpt.core/src/org/eclipse/jpt/core/internal/AbstractJpaProject.java b/jpa/plugins/org.eclipse.jpt.core/src/org/eclipse/jpt/core/internal/AbstractJpaProject.java
index 08e4a79..66dc03c 100644
--- a/jpa/plugins/org.eclipse.jpt.core/src/org/eclipse/jpt/core/internal/AbstractJpaProject.java
+++ b/jpa/plugins/org.eclipse.jpt.core/src/org/eclipse/jpt/core/internal/AbstractJpaProject.java
@@ -656,7 +656,7 @@
 	public JpaXmlResource getPersistenceXmlResource() {
 		return (JpaXmlResource) this.getResourceModel(
 				JptCorePlugin.DEFAULT_PERSISTENCE_XML_FILE_PATH,
-				JptCorePlugin.PERSISTENCE_XML_CONTENT_TYPE
+				JptCorePlugin.PERSISTENCE_FILE_CONTENT_TYPE
 			);
 	}
 
@@ -665,7 +665,7 @@
 	}
 
 	public JpaXmlResource getMappingFileXmlResource(String fileName) {
-		return (JpaXmlResource) this.getResourceModel(fileName, JptCorePlugin.ORM_XML_CONTENT_TYPE);
+		return (JpaXmlResource) this.getResourceModel(fileName, JptCorePlugin.MAPPING_FILE_CONTENT_TYPE);
 	}
 
 	/**
diff --git a/jpa/plugins/org.eclipse.jpt.core/src/org/eclipse/jpt/core/internal/context/orm/AbstractOrmXml.java b/jpa/plugins/org.eclipse.jpt.core/src/org/eclipse/jpt/core/internal/context/orm/AbstractOrmXml.java
index 79fccfa..475d3d4 100644
--- a/jpa/plugins/org.eclipse.jpt.core/src/org/eclipse/jpt/core/internal/context/orm/AbstractOrmXml.java
+++ b/jpa/plugins/org.eclipse.jpt.core/src/org/eclipse/jpt/core/internal/context/orm/AbstractOrmXml.java
@@ -39,7 +39,7 @@
 	
 	public AbstractOrmXml(MappingFileRef parent, JpaXmlResource resource) {
 		super(parent);
-		if (!resource.getContentType().isKindOf(JptCorePlugin.ORM_XML_CONTENT_TYPE)) {
+		if (!resource.getContentType().isKindOf(JptCorePlugin.MAPPING_FILE_CONTENT_TYPE)) {
 			throw new IllegalArgumentException(resource + " does not have mapping file content type"); //$NON-NLS-1$
 		}
 		this.xmlResource = resource;
@@ -139,7 +139,7 @@
 	// ********** updating **********
 	
 	public void update(JpaXmlResource resource) {		
-		if (!resource.getContentType().isKindOf(JptCorePlugin.ORM_XML_CONTENT_TYPE)) {
+		if (!resource.getContentType().isKindOf(JptCorePlugin.MAPPING_FILE_CONTENT_TYPE)) {
 			throw new IllegalArgumentException(resource + " does not have mapping file content type"); //$NON-NLS-1$
 		}
 		this.xmlResource = resource;