[400892] Intern all CDOIDs

https://bugs.eclipse.org/bugs/show_bug.cgi?id=400892

20 files changed, 1126 insertions, 915 deletions

diff --git a/plugins/org.eclipse.emf.cdo.common/src/org/eclipse/emf/cdo/common/id/CDOID.java b/plugins/org.eclipse.emf.cdo.common/src/org/eclipse/emf/cdo/common/id/CDOID.java
index be107471c3..81c774b0b2 100644
--- a/plugins/org.eclipse.emf.cdo.common/src/org/eclipse/emf/cdo/common/id/CDOID.java
+++ b/plugins/org.eclipse.emf.cdo.common/src/org/eclipse/emf/cdo/common/id/CDOID.java
@@ -21,14 +21,14 @@ import java.lang.reflect.Array;
 
 /**
  * Identifies CDO objects uniquely in a CDO {@link CDOCommonRepository repository}.
- * 
+ *
  * @author Eike Stepper
  * @noextend This interface is not intended to be extended by clients.
  * @noimplement This interface is not intended to be implemented by clients.
  * @apiviz.landmark
  * @apiviz.has {@link CDOID.Type}
  */
-public interface CDOID extends Serializable, Comparable<CDOID>
+public interface CDOID extends Comparable<CDOID>, Serializable
 {
   public static final CDOID NULL = org.eclipse.emf.cdo.internal.common.id.CDOIDNullImpl.INSTANCE;
 
@@ -42,7 +42,9 @@ public interface CDOID extends Serializable, Comparable<CDOID>
 
   /**
    * @since 3.0
+   * @deprecated
    */
+  @Deprecated
   public boolean isDangling();
 
   /**
@@ -57,7 +59,7 @@ public interface CDOID extends Serializable, Comparable<CDOID>
 
   /**
    * Enumerates the possible types of CDO {@link CDOID IDs}.
-   * 
+   *
    * @author Eike Stepper
    */
   public enum Type
@@ -131,7 +133,7 @@ public interface CDOID extends Serializable, Comparable<CDOID>
 
   /**
    * Enumerates the possible <b>sub</b> types of CDO {@link CDOID IDs} with the main type {@link Type#OBJECT OBJECT}.
-   * 
+   *
    * @author Eike Stepper
    * @since 3.0
    */
diff --git a/plugins/org.eclipse.emf.cdo.common/src/org/eclipse/emf/cdo/common/id/CDOIDString.java b/plugins/org.eclipse.emf.cdo.common/src/org/eclipse/emf/cdo/common/id/CDOIDString.java
new file mode 100644
index 0000000000..070f326d0e
--- /dev/null
+++ b/plugins/org.eclipse.emf.cdo.common/src/org/eclipse/emf/cdo/common/id/CDOIDString.java
@@ -0,0 +1,25 @@
+/*
+ * Copyright (c) 2004 - 2012 Eike Stepper (Berlin, Germany) and others.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ *
+ * Contributors:
+ *    Simon McDuff - initial API and implementation
+ *    Eike Stepper - maintenance
+ */
+package org.eclipse.emf.cdo.common.id;
+
+/**
+ * A {@link CDOID} with a {@link String} value.
+ *
+ * @author Eike Stepper
+ * @since 4.2
+ * @noextend This interface is not intended to be extended by clients.
+ * @noimplement This interface is not intended to be implemented by clients.
+ */
+public interface CDOIDString extends CDOID
+{
+  public String getStringValue();
+}
diff --git a/plugins/org.eclipse.emf.cdo.common/src/org/eclipse/emf/cdo/common/id/CDOIDUtil.java b/plugins/org.eclipse.emf.cdo.common/src/org/eclipse/emf/cdo/common/id/CDOIDUtil.java
index 094cfd9a0e..8e1c6b7398 100644
--- a/plugins/org.eclipse.emf.cdo.common/src/org/eclipse/emf/cdo/common/id/CDOIDUtil.java
+++ b/plugins/org.eclipse.emf.cdo.common/src/org/eclipse/emf/cdo/common/id/CDOIDUtil.java
@@ -17,6 +17,8 @@ import org.eclipse.emf.cdo.common.branch.CDOBranch;
 import org.eclipse.emf.cdo.common.id.CDOID.ObjectType;
 import org.eclipse.emf.cdo.common.id.CDOID.Type;
 import org.eclipse.emf.cdo.common.model.CDOClassifierRef;
+import org.eclipse.emf.cdo.common.protocol.CDODataInput;
+import org.eclipse.emf.cdo.common.protocol.CDODataOutput;
 import org.eclipse.emf.cdo.common.revision.CDOIDAndBranch;
 import org.eclipse.emf.cdo.common.revision.CDOIDAndVersion;
 import org.eclipse.emf.cdo.internal.common.bundle.OM;
@@ -32,9 +34,6 @@ import org.eclipse.emf.cdo.internal.common.messages.Messages;
 import org.eclipse.emf.cdo.internal.common.revision.CDOIDAndBranchImpl;
 import org.eclipse.emf.cdo.internal.common.revision.CDOIDAndVersionImpl;
 import org.eclipse.emf.cdo.spi.common.id.AbstractCDOID;
-import org.eclipse.emf.cdo.spi.common.id.AbstractCDOIDByteArray;
-import org.eclipse.emf.cdo.spi.common.id.AbstractCDOIDLong;
-import org.eclipse.emf.cdo.spi.common.id.AbstractCDOIDString;
 import org.eclipse.emf.cdo.spi.common.id.InternalCDOIDObject;
 
 import org.eclipse.net4j.util.ObjectUtil;
@@ -61,6 +60,30 @@ public final class CDOIDUtil
   }
 
   /**
+   * @since 4.0
+   */
+  public static CDOIDAndVersion createIDAndVersion(CDOID id, int version)
+  {
+    return new CDOIDAndVersionImpl(id, version);
+  }
+
+  /**
+   * @since 4.0
+   */
+  public static CDOIDAndVersion createIDAndVersion(CDOIDAndVersion source)
+  {
+    return createIDAndVersion(source.getID(), source.getVersion());
+  }
+
+  /**
+   * @since 4.0
+   */
+  public static CDOIDAndBranch createIDAndBranch(CDOID id, CDOBranch branch)
+  {
+    return new CDOIDAndBranchImpl(id, branch);
+  }
+
+  /**
    * @since 4.2
    */
   public static CDOID getCDOID(Object object)
@@ -96,18 +119,23 @@ public final class CDOIDUtil
   {
     if (id == null)
     {
-      return AbstractCDOIDLong.NULL_VALUE;
+      return 0L;
     }
 
     switch (id.getType())
     {
     case NULL:
-      return AbstractCDOIDLong.NULL_VALUE;
+      return 0L;
 
     case OBJECT:
-      if (id instanceof AbstractCDOIDLong)
+      if (id instanceof CDOIDObjectLongImpl)
       {
-        return ((AbstractCDOIDLong)id).getLongValue();
+        return ((CDOIDObjectLongImpl)id).getLongValue();
+      }
+
+      if (id instanceof CDOIDObjectLongWithClassifierImpl)
+      {
+        return ((CDOIDObjectLongWithClassifierImpl)id).getLongValue();
       }
 
       throw new IllegalArgumentException(MessageFormat.format(
@@ -131,42 +159,12 @@ public final class CDOIDUtil
    */
   public static String getString(CDOID id)
   {
-    if (id == null)
+    if (id instanceof CDOIDString)
     {
-      return AbstractCDOIDString.NULL_VALUE;
+      return ((CDOIDString)id).getStringValue();
     }
 
-    switch (id.getType())
-    {
-    case NULL:
-      return AbstractCDOIDString.NULL_VALUE;
-
-    case OBJECT:
-      if (id instanceof AbstractCDOIDString)
-      {
-        return ((AbstractCDOIDString)id).getStringValue();
-      }
-
-      throw new IllegalArgumentException(MessageFormat.format(
-          Messages.getString("CDOIDUtil.0"), id.getClass().getName())); //$NON-NLS-1$
-
-    case TEMP_OBJECT:
-      throw new IllegalArgumentException(Messages.getString("CDOIDUtil.1")); //$NON-NLS-1$
-
-    case EXTERNAL_OBJECT:
-    case EXTERNAL_TEMP_OBJECT:
-      if (id instanceof CDOIDExternalImpl)
-      {
-        return ((CDOIDExternalImpl)id).getURI();
-      }
-
-      throw new IllegalArgumentException(MessageFormat.format(
-          Messages.getString("CDOIDUtil.0"), id.getClass().getName())); //$NON-NLS-1$
-
-    default:
-      throw new IllegalArgumentException(MessageFormat.format(
-          Messages.getString("CDOIDUtil.3"), id.getClass().getName())); //$NON-NLS-1$
-    }
+    return null;
   }
 
   /**
@@ -174,29 +172,12 @@ public final class CDOIDUtil
    */
   public static byte[] getByteArray(CDOID id)
   {
-    if (id == null)
+    if (id instanceof CDOIDObjectUUIDImpl)
     {
-      return null;
+      return ((CDOIDObjectUUIDImpl)id).getByteArrayValue();
     }
 
-    switch (id.getType())
-    {
-    case NULL:
-      return null;
-
-    case OBJECT:
-      if (id instanceof AbstractCDOIDByteArray)
-      {
-        return ((AbstractCDOIDByteArray)id).getByteArrayValue();
-      }
-
-      throw new IllegalArgumentException(MessageFormat.format(
-          Messages.getString("CDOIDUtil.0"), id.getClass().getName())); //$NON-NLS-1$
-
-    default:
-      throw new IllegalArgumentException(MessageFormat.format(
-          Messages.getString("CDOIDUtil.3"), id.getClass().getName())); //$NON-NLS-1$
-    }
+    return null;
   }
 
   /**
@@ -214,7 +195,7 @@ public final class CDOIDUtil
 
   public static CDOIDTemp createTempObject(int value)
   {
-    return new CDOIDTempObjectImpl(value);
+    return CDOIDTempObjectImpl.create(value);
   }
 
   /**
@@ -222,25 +203,25 @@ public final class CDOIDUtil
    */
   public static CDOIDExternal createTempObjectExternal(String uri)
   {
-    return new CDOIDTempObjectExternalImpl(uri);
+    return CDOIDTempObjectExternalImpl.create(uri);
   }
 
   public static CDOID createLong(long value)
   {
-    if (value == AbstractCDOIDLong.NULL_VALUE)
+    if (value == 0L)
     {
       return CDOID.NULL;
     }
 
-    return new CDOIDObjectLongImpl(value);
+    return CDOIDObjectLongImpl.create(value);
   }
 
   /**
-   * @since 3.0
+   * @since 4.2
    */
-  public static CDOID createLongWithClassifier(CDOClassifierRef classifierRef, long value)
+  public static CDOID createLongWithClassifier(long value, CDOClassifierRef classifierRef)
   {
-    return new CDOIDObjectLongWithClassifierImpl(classifierRef, value);
+    return CDOIDObjectLongWithClassifierImpl.create(value, classifierRef);
   }
 
   /**
@@ -248,15 +229,15 @@ public final class CDOIDUtil
    */
   public static CDOID createString(String value)
   {
-    return new CDOIDObjectStringImpl(value);
+    return CDOIDObjectStringImpl.create(value);
   }
 
   /**
-   * @since 3.0
+   * @since 4.2
    */
-  public static CDOID createStringWithClassifier(CDOClassifierRef classifierRef, String value)
+  public static CDOID createStringWithClassifier(String value, CDOClassifierRef classifierRef)
   {
-    return new CDOIDObjectStringWithClassifierImpl(classifierRef, value);
+    return CDOIDObjectStringWithClassifierImpl.create(value, classifierRef);
   }
 
   /**
@@ -264,7 +245,7 @@ public final class CDOIDUtil
    */
   public static CDOID createUUID(byte[] value)
   {
-    return new CDOIDObjectUUIDImpl(value);
+    return CDOIDObjectUUIDImpl.create(value);
   }
 
   /**
@@ -298,82 +279,7 @@ public final class CDOIDUtil
    */
   public static CDOIDExternal createExternal(String uri)
   {
-    return new CDOIDExternalImpl(uri);
-  }
-
-  /**
-   * @since 4.0
-   */
-  public static CDOIDAndVersion createIDAndVersion(CDOID id, int version)
-  {
-    return new CDOIDAndVersionImpl(id, version);
-  }
-
-  /**
-   * @since 4.0
-   */
-  public static CDOIDAndVersion createIDAndVersion(CDOIDAndVersion source)
-  {
-    return createIDAndVersion(source.getID(), source.getVersion());
-  }
-
-  /**
-   * @since 4.0
-   */
-  public static CDOIDAndBranch createIDAndBranch(CDOID id, CDOBranch branch)
-  {
-    return new CDOIDAndBranchImpl(id, branch);
-  }
-
-  /**
-   * Creates the correct implementation class for the passed {@link CDOID.ObjectType}.
-   *
-   * @param subType
-   *          the subType for which to create an empty CDOID instance
-   * @return the instance of CDOIDObject which represents the subtype.
-   * @since 3.0
-   */
-  public static AbstractCDOID createCDOIDObject(CDOID.ObjectType subType)
-  {
-    if (subType == null)
-    {
-      throw new IllegalArgumentException("SubType may not be null");
-    }
-
-    InternalCDOIDObject id;
-    switch (subType)
-    {
-    case LONG:
-      id = new CDOIDObjectLongImpl();
-      break;
-
-    case STRING:
-      id = new CDOIDObjectStringImpl();
-      break;
-
-    case LONG_WITH_CLASSIFIER:
-      id = new CDOIDObjectLongWithClassifierImpl();
-      break;
-
-    case STRING_WITH_CLASSIFIER:
-      id = new CDOIDObjectStringWithClassifierImpl();
-      break;
-
-    case UUID:
-      id = new CDOIDObjectUUIDImpl();
-      break;
-
-    default:
-      throw new IllegalArgumentException("Subtype " + subType.name() + " not supported");
-    }
-
-    if (id.getSubType() != subType)
-    {
-      throw new IllegalStateException("Subtype of created id " + id + " is unequal (" + id.getSubType().name()
-          + ") to requested subtype " + subType.name());
-    }
-
-    return (AbstractCDOID)id;
+    return CDOIDExternalImpl.create(uri);
   }
 
   /**
@@ -437,19 +343,13 @@ public final class CDOIDUtil
       return CDOID.NULL;
 
     case TEMP_OBJECT:
-      return new CDOIDTempObjectImpl(Integer.valueOf(fragment));
+      return CDOIDTempObjectImpl.create(Integer.valueOf(fragment));
 
     case EXTERNAL_OBJECT:
-      return new CDOIDExternalImpl(fragment);
+      return CDOIDExternalImpl.create(fragment);
 
     case EXTERNAL_TEMP_OBJECT:
-      return new CDOIDTempObjectExternalImpl(fragment);
-
-    case OBJECT:
-    {
-      // Normally this case should not occur (is an OBJECT subtype).
-      throw new IllegalArgumentException();
-    }
+      return CDOIDTempObjectExternalImpl.create(fragment);
 
     default:
       throw new IllegalArgumentException(MessageFormat.format(Messages.getString("CDOIDUtil.5"), uriFragment)); //$NON-NLS-1$
@@ -458,15 +358,32 @@ public final class CDOIDUtil
 
   private static CDOID readCDOIDObject(String fragment, CDOID.ObjectType subType)
   {
-    AbstractCDOID id = createCDOIDObject(subType);
-    id.read(fragment);
-    return id;
+    switch (subType)
+    {
+    case LONG:
+      return CDOIDObjectLongImpl.create(fragment);
+
+    case STRING:
+      return CDOIDObjectStringImpl.create(fragment);
+
+    case LONG_WITH_CLASSIFIER:
+      return CDOIDObjectLongWithClassifierImpl.create(fragment);
+
+    case STRING_WITH_CLASSIFIER:
+      return CDOIDObjectStringWithClassifierImpl.create(fragment);
+
+    case UUID:
+      return CDOIDObjectUUIDImpl.create(fragment);
+
+    default:
+      throw new IllegalArgumentException("Subtype " + subType.name() + " not supported");
+    }
   }
 
   /**
-   * @since 4.1
+   * @since 4.2
    */
-  public static void write(ExtendedDataOutput out, CDOID id) throws IOException
+  public static void write(CDODataOutput out, CDOID id) throws IOException
   {
     if (id == null)
     {
@@ -502,9 +419,9 @@ public final class CDOIDUtil
   }
 
   /**
-   * @since 4.1
+   * @since 4.2
    */
-  public static CDOID read(ExtendedDataInput in) throws IOException
+  public static CDOID read(CDODataInput in) throws IOException
   {
     byte ordinal = in.readByte();
 
@@ -538,30 +455,20 @@ public final class CDOIDUtil
       return CDOID.NULL;
 
     case TEMP_OBJECT:
-      return new CDOIDTempObjectImpl(in.readInt());
+      return CDOIDTempObjectImpl.create(in.readInt());
 
     case EXTERNAL_OBJECT:
-      return new CDOIDExternalImpl(in.readString());
+      return CDOIDExternalImpl.create(in.readString());
 
     case EXTERNAL_TEMP_OBJECT:
-      return new CDOIDTempObjectExternalImpl(in.readString());
-
-    case OBJECT:
-    {
-      // should normally not occur is handled by
-      // readCDOIDObject, code remains here
-      // for backward compatibility
-      AbstractCDOID id = new CDOIDObjectLongImpl();
-      id.read(in);
-      return id;
-    }
+      return CDOIDTempObjectExternalImpl.create(in.readString());
 
     default:
       throw new IOException("Illegal type: " + type);
     }
   }
 
-  private static CDOID readCDOIDObject(ExtendedDataInput in, int subTypeOrdinal) throws IOException
+  private static CDOID readCDOIDObject(CDODataInput in, int subTypeOrdinal) throws IOException
   {
     if (TRACER.isEnabled())
     {
@@ -576,13 +483,35 @@ public final class CDOIDUtil
         subType = ex.getMessage();
       }
 
-      TRACER.format("Reading CDOIDObject of sub type {0} ({1})", subTypeOrdinal, subType); //$NON-NLS-1$
+      TRACER.format("Reading CDOIDObject of subtype {0} ({1})", subTypeOrdinal, subType); //$NON-NLS-1$
     }
 
     CDOID.ObjectType subType = CDOID.ObjectType.values()[subTypeOrdinal];
-    AbstractCDOID id = CDOIDUtil.createCDOIDObject(subType);
-    id.read(in);
-    return id;
+    if (subType == null)
+    {
+      throw new IllegalArgumentException("Subtype may not be null");
+    }
+
+    switch (subType)
+    {
+    case LONG:
+      return CDOIDObjectLongImpl.create(in);
+
+    case STRING:
+      return CDOIDObjectStringImpl.create(in);
+
+    case LONG_WITH_CLASSIFIER:
+      return CDOIDObjectLongWithClassifierImpl.create(in);
+
+    case STRING_WITH_CLASSIFIER:
+      return CDOIDObjectStringWithClassifierImpl.create(in);
+
+    case UUID:
+      return CDOIDObjectUUIDImpl.create(in);
+
+    default:
+      throw new IllegalArgumentException("Subtype " + subType.name() + " not supported");
+    }
   }
 
   /**
@@ -602,4 +531,59 @@ public final class CDOIDUtil
 
     return ObjectUtil.equals(id1, id2);
   }
+
+  /**
+   * @since 3.0
+   * @deprecated As of 4.2 use {@link #createLongWithClassifier(long, CDOClassifierRef)}.
+   */
+  @Deprecated
+  public static CDOID createLongWithClassifier(CDOClassifierRef classifierRef, long value)
+  {
+    return createLongWithClassifier(value, classifierRef);
+  }
+
+  /**
+   * @since 3.0
+   * @deprecated As of 4.2 use {@link #createStringWithClassifier(String, CDOClassifierRef)}.
+   */
+  @Deprecated
+  public static CDOID createStringWithClassifier(CDOClassifierRef classifierRef, String value)
+  {
+    return createStringWithClassifier(value, classifierRef);
+  }
+
+  /**
+   * Creates the correct implementation class for the passed {@link CDOID.ObjectType}.
+   *
+   * @param subType
+   *          the subType for which to create an empty CDOID instance
+   * @return the instance of CDOIDObject which represents the subtype.
+   * @since 3.0
+   * @deprecated As of 4.2 no longer supported. IDs can't be created without a value anymore.
+   */
+  @Deprecated
+  public static AbstractCDOID createCDOIDObject(CDOID.ObjectType subType)
+  {
+    throw new UnsupportedOperationException();
+  }
+
+  /**
+   * @since 4.1
+   * @deprecated As of 4.2 use {@link #write(CDODataOutput, CDOID)}.
+   */
+  @Deprecated
+  public static void write(ExtendedDataOutput out, CDOID id) throws IOException
+  {
+    write((CDODataOutput)out, id);
+  }
+
+  /**
+   * @since 4.1
+   * @deprecated As of 4.2 use {@link #read(CDODataInput)}.
+   */
+  @Deprecated
+  public static CDOID read(ExtendedDataInput in) throws IOException
+  {
+    return read((CDODataInput)in);
+  }
 }
diff --git a/plugins/org.eclipse.emf.cdo.common/src/org/eclipse/emf/cdo/common/model/CDOClassifierRef.java b/plugins/org.eclipse.emf.cdo.common/src/org/eclipse/emf/cdo/common/model/CDOClassifierRef.java
index 7d7f8cfa71..40149185d8 100644
--- a/plugins/org.eclipse.emf.cdo.common/src/org/eclipse/emf/cdo/common/model/CDOClassifierRef.java
+++ b/plugins/org.eclipse.emf.cdo.common/src/org/eclipse/emf/cdo/common/model/CDOClassifierRef.java
@@ -20,16 +20,19 @@ import org.eclipse.emf.ecore.EClassifier;
 import org.eclipse.emf.ecore.EPackage;
 
 import java.io.IOException;
+import java.io.Serializable;
 import java.text.MessageFormat;
 
 /**
  * References an {@link EClassifier}.
- * 
+ *
  * @author Eike Stepper
  * @since 2.0
  */
-public final class CDOClassifierRef
+public final class CDOClassifierRef implements Serializable
 {
+  private static final long serialVersionUID = 1L;
+
   public static final String URI_SEPARATOR = "#"; //$NON-NLS-1$
 
   private String packageURI;
@@ -147,7 +150,7 @@ public final class CDOClassifierRef
 
   /**
    * Provides {@link CDOClassifierRef classifier references}.
-   * 
+   *
    * @author Eike Stepper
    * @since 3.0
    * @apiviz.uses {@link CDOClassifierRef} - - provides
diff --git a/plugins/org.eclipse.emf.cdo.common/src/org/eclipse/emf/cdo/internal/common/id/CDOIDExternalImpl.java b/plugins/org.eclipse.emf.cdo.common/src/org/eclipse/emf/cdo/internal/common/id/CDOIDExternalImpl.java
index f3491c1e5c..8717d8ed7e 100644
--- a/plugins/org.eclipse.emf.cdo.common/src/org/eclipse/emf/cdo/internal/common/id/CDOIDExternalImpl.java
+++ b/plugins/org.eclipse.emf.cdo.common/src/org/eclipse/emf/cdo/internal/common/id/CDOIDExternalImpl.java
@@ -6,53 +6,70 @@
  * http://www.eclipse.org/legal/epl-v10.html
  *
  * Contributors:
- *    Simon McDuff - initial API and implementation
- *    Eike Stepper - maintenance
+ *    Eike Stepper - initial API and implementation
  */
 package org.eclipse.emf.cdo.internal.common.id;
 
 import org.eclipse.emf.cdo.common.id.CDOID;
 import org.eclipse.emf.cdo.common.id.CDOIDExternal;
+import org.eclipse.emf.cdo.common.id.CDOIDString;
+import org.eclipse.emf.cdo.common.protocol.CDODataInput;
+import org.eclipse.emf.cdo.common.protocol.CDODataOutput;
 import org.eclipse.emf.cdo.spi.common.id.AbstractCDOID;
 
-import org.eclipse.net4j.util.ObjectUtil;
-import org.eclipse.net4j.util.io.ExtendedDataInput;
-import org.eclipse.net4j.util.io.ExtendedDataOutput;
+import org.eclipse.net4j.util.CheckUtil;
+import org.eclipse.net4j.util.ref.Interner;
 
 import java.io.IOException;
+import java.io.ObjectStreamException;
 
 /**
- * @author Simon McDuff
+ * @author Eike Stepper
+ * @since 2.0
  */
-public class CDOIDExternalImpl extends AbstractCDOID implements CDOIDExternal
+public final class CDOIDExternalImpl extends AbstractCDOID implements CDOIDExternal, CDOIDString
 {
   private static final long serialVersionUID = 1L;
 
-  private String uri;
+  private static final StringInterner INTERNER = new StringInterner();
 
-  public CDOIDExternalImpl(String uri)
+  private final String uri;
+
+  private CDOIDExternalImpl(String uri)
   {
+    CheckUtil.checkArg(uri, "Null not allowed");
     this.uri = uri;
   }
 
-  public Type getType()
+  @Override
+  public void write(CDODataOutput out) throws IOException
   {
-    return Type.EXTERNAL_OBJECT;
+    out.writeString(uri);
   }
 
-  public boolean isDangling()
+  public String toURIFragment()
   {
-    return false;
+    return uri;
   }
 
-  public boolean isExternal()
+  public String getURI()
   {
-    return true;
+    return uri;
   }
 
-  public boolean isNull()
+  public String getStringValue()
   {
-    return false;
+    return uri;
+  }
+
+  public Type getType()
+  {
+    return Type.EXTERNAL_OBJECT;
+  }
+
+  public boolean isExternal()
+  {
+    return true;
   }
 
   public boolean isObject()
@@ -65,67 +82,71 @@ public class CDOIDExternalImpl extends AbstractCDOID implements CDOIDExternal
     return false;
   }
 
-  public String getURI()
+  @Override
+  public int hashCode()
   {
-    return uri;
+    return uri.hashCode();
   }
 
   @Override
   public String toString()
   {
-    return "oid:" + toURIFragment(); //$NON-NLS-1$
+    return "oid:" + uri; //$NON-NLS-1$
   }
 
   @Override
-  public void read(String fragmentPart)
+  protected int doCompareTo(CDOID o) throws ClassCastException
   {
-    uri = fragmentPart;
+    return uri.compareTo(((CDOIDExternalImpl)o).uri);
   }
 
-  @Override
-  public void read(ExtendedDataInput in) throws IOException
+  private Object readResolve() throws ObjectStreamException
   {
-    uri = in.readString();
+    return create(uri);
   }
 
-  @Override
-  public void write(ExtendedDataOutput out) throws IOException
+  private static int getHashCode(String uri)
   {
-    out.writeString(uri);
+    return uri.hashCode();
   }
 
-  public String toURIFragment()
+  public static CDOIDExternalImpl create(String uri)
   {
-    return uri;
+    return INTERNER.intern(uri);
   }
 
-  @Override
-  public boolean equals(Object obj)
+  public static CDOIDExternalImpl create(CDODataInput in) throws IOException
+  {
+    String uri = in.readString();
+    return create(uri);
+  }
+
+  /**
+   * @author Eike Stepper
+   */
+  private static final class StringInterner extends Interner<CDOIDExternalImpl>
   {
-    if (obj == this)
+    public synchronized CDOIDExternalImpl intern(String uri)
     {
-      return true;
+      int hashCode = getHashCode(uri);
+      for (Entry<CDOIDExternalImpl> entry = getEntry(hashCode); entry != null; entry = entry.getNextEntry())
+      {
+        CDOIDExternalImpl id = entry.get();
+        if (id != null && id.uri.equals(uri))
+        {
+          return id;
+        }
+      }
+
+      CDOIDExternalImpl id = new CDOIDExternalImpl(uri);
+      addEntry(createEntry(id, hashCode));
+      return id;
     }
 
-    // Could CDOIDTempObjectExternalImpl and CDOIDExternalImpl have the same uri. We don't want to mixed them.
-    if (obj != null && obj.getClass() == getClass())
+    @Override
+    protected int hashCode(CDOIDExternalImpl id)
     {
-      CDOIDExternal that = (CDOIDExternal)obj;
-      return ObjectUtil.equals(getURI(), that.getURI());
+      return getHashCode(id.uri);
     }
-
-    return false;
-  }
-
-  @Override
-  public int hashCode()
-  {
-    return getClass().hashCode() ^ uri.hashCode();
-  }
-
-  @Override
-  protected int doCompareTo(CDOID o) throws ClassCastException
-  {
-    return getURI().compareTo(((CDOIDExternalImpl)o).getURI());
   }
 }
diff --git a/plugins/org.eclipse.emf.cdo.common/src/org/eclipse/emf/cdo/internal/common/id/CDOIDNullImpl.java b/plugins/org.eclipse.emf.cdo.common/src/org/eclipse/emf/cdo/internal/common/id/CDOIDNullImpl.java
index 836db08673..eeb2c3c89e 100644
--- a/plugins/org.eclipse.emf.cdo.common/src/org/eclipse/emf/cdo/internal/common/id/CDOIDNullImpl.java
+++ b/plugins/org.eclipse.emf.cdo.common/src/org/eclipse/emf/cdo/internal/common/id/CDOIDNullImpl.java
@@ -15,93 +15,70 @@ package org.eclipse.emf.cdo.internal.common.id;
 import org.eclipse.emf.cdo.common.id.CDOID;
 import org.eclipse.emf.cdo.common.id.CDOIDObject;
 import org.eclipse.emf.cdo.common.id.CDOIDTemp;
+import org.eclipse.emf.cdo.common.protocol.CDODataOutput;
 import org.eclipse.emf.cdo.spi.common.id.AbstractCDOID;
 
-import org.eclipse.net4j.util.io.ExtendedDataInput;
-import org.eclipse.net4j.util.io.ExtendedDataOutput;
-
 import java.io.IOException;
+import java.io.ObjectStreamException;
 
 /**
  * @author Eike Stepper
  */
 public final class CDOIDNullImpl extends AbstractCDOID implements CDOIDTemp, CDOIDObject
 {
-  public static final CDOIDNullImpl INSTANCE = new CDOIDNullImpl();
-
   private static final long serialVersionUID = 1L;
 
+  public static final CDOIDNullImpl INSTANCE = new CDOIDNullImpl();
+
   private CDOIDNullImpl()
   {
   }
 
-  public Type getType()
+  public int getIntValue()
   {
-    return Type.NULL;
+    return 0;
   }
 
-  public boolean isDangling()
+  public long getLongValue()
   {
-    return false;
+    return 0L;
   }
 
-  public boolean isExternal()
+  @Override
+  public void write(CDODataOutput out) throws IOException
   {
-    return false;
+    // Do nothing
   }
 
-  public boolean isNull()
+  public String toURIFragment()
   {
-    return true;
+    return "NULL"; //$NON-NLS-1$
   }
 
-  public boolean isObject()
+  public Type getType()
   {
-    return false;
+    return Type.NULL;
   }
 
-  public boolean isTemporary()
+  public boolean isExternal()
   {
     return false;
   }
 
-  public int getIntValue()
-  {
-    return 0;
-  }
-
-  public long getLongValue()
-  {
-    return 0L;
-  }
-
-  public String toURIFragment()
-  {
-    return "NULL"; //$NON-NLS-1$
-  }
-
   @Override
-  public void read(String fragmentPart)
-  {
-    // Do nothing
-  }
-
-  @Override
-  public void read(ExtendedDataInput in) throws IOException
+  public boolean isNull()
   {
-    // Do nothing
+    return true;
   }
 
-  @Override
-  public void write(ExtendedDataOutput out) throws IOException
+  public boolean isObject()
   {
-    // Do nothing
+    return false;
   }
 
-  @Override
-  public boolean equals(Object obj)
+  public boolean isTemporary()
   {
-    return obj == INSTANCE;
+    return false;
   }
 
   @Override
@@ -119,7 +96,11 @@ public final class CDOIDNullImpl extends AbstractCDOID implements CDOIDTemp, CDO
   @Override
   protected int doCompareTo(CDOID o) throws ClassCastException
   {
-    ((CDOIDNullImpl)o).getIntValue(); // Possibly throw ClassCastException
     return 0; // NULL == NULL
   }
+
+  private Object readResolve() throws ObjectStreamException
+  {
+    return INSTANCE;
+  }
 }
diff --git a/plugins/org.eclipse.emf.cdo.common/src/org/eclipse/emf/cdo/internal/common/id/CDOIDObjectLongImpl.java b/plugins/org.eclipse.emf.cdo.common/src/org/eclipse/emf/cdo/internal/common/id/CDOIDObjectLongImpl.java
index a4d17b3855..48f267696c 100644
--- a/plugins/org.eclipse.emf.cdo.common/src/org/eclipse/emf/cdo/internal/common/id/CDOIDObjectLongImpl.java
+++ b/plugins/org.eclipse.emf.cdo.common/src/org/eclipse/emf/cdo/internal/common/id/CDOIDObjectLongImpl.java
@@ -11,42 +11,58 @@
 package org.eclipse.emf.cdo.internal.common.id;
 
 import org.eclipse.emf.cdo.common.id.CDOID;
-import org.eclipse.emf.cdo.spi.common.id.AbstractCDOIDLong;
+import org.eclipse.emf.cdo.common.protocol.CDODataInput;
+import org.eclipse.emf.cdo.common.protocol.CDODataOutput;
+import org.eclipse.emf.cdo.spi.common.id.AbstractCDOID;
 import org.eclipse.emf.cdo.spi.common.id.InternalCDOIDObject;
 
+import org.eclipse.net4j.util.CheckUtil;
+import org.eclipse.net4j.util.ObjectUtil;
+import org.eclipse.net4j.util.ref.Interner;
+
+import java.io.IOException;
+import java.io.ObjectStreamException;
+
 /**
  * @author Eike Stepper
  * @since 2.0
  */
-public class CDOIDObjectLongImpl extends AbstractCDOIDLong implements InternalCDOIDObject
+public final class CDOIDObjectLongImpl extends AbstractCDOID implements InternalCDOIDObject
 {
   private static final long serialVersionUID = 1L;
 
-  public CDOIDObjectLongImpl()
+  private static final LongInterner INTERNER = new LongInterner();
+
+  private final long value;
+
+  private CDOIDObjectLongImpl(long value)
   {
+    CheckUtil.checkArg(value != 0L, "Zero not allowed");
+    this.value = value;
   }
 
-  public CDOIDObjectLongImpl(long value)
+  public long getLongValue()
   {
-    super(value);
+    return value;
   }
 
-  public Type getType()
+  @Override
+  public void write(CDODataOutput out) throws IOException
   {
-    return Type.OBJECT;
+    out.writeLong(value);
   }
 
-  public boolean isDangling()
+  public String toURIFragment()
   {
-    return false;
+    return String.valueOf(value);
   }
 
-  public boolean isExternal()
+  public Type getType()
   {
-    return false;
+    return Type.OBJECT;
   }
 
-  public boolean isNull()
+  public boolean isExternal()
   {
     return false;
   }
@@ -70,14 +86,76 @@ public class CDOIDObjectLongImpl extends AbstractCDOIDLong implements InternalCD
   }
 
   @Override
+  public int hashCode()
+  {
+    return ObjectUtil.hashCode(value);
+  }
+
+  @Override
   public String toString()
   {
-    return "OID" + getLongValue(); //$NON-NLS-1$
+    return "OID" + value; //$NON-NLS-1$
   }
 
   @Override
   protected int doCompareTo(CDOID o) throws ClassCastException
   {
-    return new Long(getLongValue()).compareTo(((CDOIDObjectLongImpl)o).getLongValue());
+    return new Long(value).compareTo(((CDOIDObjectLongImpl)o).value);
+  }
+
+  private Object readResolve() throws ObjectStreamException
+  {
+    return create(value);
+  }
+
+  private static int getHashCode(long value)
+  {
+    return ObjectUtil.hashCode(value);
+  }
+
+  public static CDOIDObjectLongImpl create(long value)
+  {
+    return INTERNER.intern(value);
+  }
+
+  public static CDOIDObjectLongImpl create(CDODataInput in) throws IOException
+  {
+    long value = in.readLong();
+    return create(value);
+  }
+
+  public static CDOIDObjectLongImpl create(String fragmentPart)
+  {
+    long value = Long.parseLong(fragmentPart);
+    return create(value);
+  }
+
+  /**
+   * @author Eike Stepper
+   */
+  private static final class LongInterner extends Interner<CDOIDObjectLongImpl>
+  {
+    public synchronized CDOIDObjectLongImpl intern(long value)
+    {
+      int hashCode = getHashCode(value);
+      for (Entry<CDOIDObjectLongImpl> entry = getEntry(hashCode); entry != null; entry = entry.getNextEntry())
+      {
+        CDOIDObjectLongImpl id = entry.get();
+        if (id != null && id.value == value)
+        {
+          return id;
+        }
+      }
+
+      CDOIDObjectLongImpl id = new CDOIDObjectLongImpl(value);
+      addEntry(createEntry(id, hashCode));
+      return id;
+    }
+
+    @Override
+    protected int hashCode(CDOIDObjectLongImpl id)
+    {
+      return getHashCode(id.value);
+    }
   }
 }
diff --git a/plugins/org.eclipse.emf.cdo.common/src/org/eclipse/emf/cdo/internal/common/id/CDOIDObjectLongWithClassifierImpl.java b/plugins/org.eclipse.emf.cdo.common/src/org/eclipse/emf/cdo/internal/common/id/CDOIDObjectLongWithClassifierImpl.java
index eb781efea5..c8f9d9893f 100644
--- a/plugins/org.eclipse.emf.cdo.common/src/org/eclipse/emf/cdo/internal/common/id/CDOIDObjectLongWithClassifierImpl.java
+++ b/plugins/org.eclipse.emf.cdo.common/src/org/eclipse/emf/cdo/internal/common/id/CDOIDObjectLongWithClassifierImpl.java
@@ -15,31 +15,41 @@ import org.eclipse.emf.cdo.common.id.CDOID;
 import org.eclipse.emf.cdo.common.model.CDOClassifierRef;
 import org.eclipse.emf.cdo.common.protocol.CDODataInput;
 import org.eclipse.emf.cdo.common.protocol.CDODataOutput;
+import org.eclipse.emf.cdo.spi.common.id.AbstractCDOID;
+import org.eclipse.emf.cdo.spi.common.id.InternalCDOIDObject;
 
+import org.eclipse.net4j.util.CheckUtil;
 import org.eclipse.net4j.util.ObjectUtil;
-import org.eclipse.net4j.util.io.ExtendedDataInput;
-import org.eclipse.net4j.util.io.ExtendedDataOutput;
+import org.eclipse.net4j.util.ref.Interner;
 
 import java.io.IOException;
+import java.io.ObjectStreamException;
 
 /**
  * @author Martin Taal
  * @since 3.0
  */
-public class CDOIDObjectLongWithClassifierImpl extends CDOIDObjectLongImpl implements CDOClassifierRef.Provider
+public final class CDOIDObjectLongWithClassifierImpl extends AbstractCDOID implements InternalCDOIDObject,
+    CDOClassifierRef.Provider
 {
   private static final long serialVersionUID = 1L;
 
-  private CDOClassifierRef classifierRef;
+  private static final LongWithClassifierInterner INTERNER = new LongWithClassifierInterner();
 
-  public CDOIDObjectLongWithClassifierImpl()
+  private final long value;
+
+  private final CDOClassifierRef classifierRef;
+
+  private CDOIDObjectLongWithClassifierImpl(long value, CDOClassifierRef classifierRef)
   {
+    CheckUtil.checkArg(value != 0L, "Zero not allowed");
+    this.value = value;
+    this.classifierRef = classifierRef;
   }
 
-  public CDOIDObjectLongWithClassifierImpl(CDOClassifierRef classifierRef, long value)
+  public long getLongValue()
   {
-    super(value);
-    this.classifierRef = classifierRef;
+    return value;
   }
 
   public CDOClassifierRef getClassifierRef()
@@ -48,98 +58,127 @@ public class CDOIDObjectLongWithClassifierImpl extends CDOIDObjectLongImpl imple
   }
 
   @Override
+  public void write(CDODataOutput out) throws IOException
+  {
+    out.writeLong(value);
+    out.writeCDOClassifierRef(classifierRef);
+  }
+
+  public String toURIFragment()
+  {
+    return classifierRef.getPackageURI() + CDOClassifierRef.URI_SEPARATOR + classifierRef.getClassifierName()
+        + CDOClassifierRef.URI_SEPARATOR + value;
+  }
+
   public Type getType()
   {
     return Type.OBJECT;
   }
 
-  @Override
   public CDOID.ObjectType getSubType()
   {
     return CDOID.ObjectType.LONG_WITH_CLASSIFIER;
   }
 
-  @Override
-  public String toURIFragment()
+  public boolean isExternal()
   {
-    return getClassifierRef().getPackageURI() + CDOClassifierRef.URI_SEPARATOR + getClassifierRef().getClassifierName()
-        + CDOClassifierRef.URI_SEPARATOR + super.toURIFragment();
+    return false;
   }
 
-  @Override
-  public void read(String fragmentPart)
+  public boolean isObject()
   {
-    // get the CDOClassifierRef part
-    int index1 = fragmentPart.indexOf(CDOClassifierRef.URI_SEPARATOR);
-    int index2 = fragmentPart.indexOf(CDOClassifierRef.URI_SEPARATOR, index1 + 1);
-    if (index1 == -1 || index2 == -1)
-    {
-      throw new IllegalArgumentException("The fragment " + fragmentPart + " is not a valid fragment");
-    }
-
-    classifierRef = new CDOClassifierRef(fragmentPart.substring(0, index1), fragmentPart.substring(index1 + 1, index2));
+    return true;
+  }
 
-    // let the super take care of the rest
-    super.read(fragmentPart.substring(index2 + 1));
+  public boolean isTemporary()
+  {
+    return false;
   }
 
   @Override
-  public void read(ExtendedDataInput in) throws IOException
+  public int hashCode()
   {
-    // TODO: change the parameter to prevent casting to CDODataInput
-    CDODataInput cdoDataInput = (CDODataInput)in;
-    classifierRef = cdoDataInput.readCDOClassifierRef();
-
-    // and let the super take care of the rest
-    super.read(in);
+    return getHashCode(value, classifierRef);
   }
 
   @Override
-  public void write(ExtendedDataOutput out) throws IOException
+  public String toString()
   {
-    // TODO: change the parameter to prevent casting to CDODataInput
-    CDODataOutput cdoDataOutput = (CDODataOutput)out;
-    cdoDataOutput.writeCDOClassifierRef(classifierRef);
-
-    // and let the super write the rest
-    super.write(out);
+    return "OID:" + toURIFragment(); //$NON-NLS-1$
   }
 
   @Override
-  public boolean equals(Object obj)
+  protected int doCompareTo(CDOID o) throws ClassCastException
   {
-    if (obj == this)
-    {
-      return true;
-    }
+    return toURIFragment().compareTo(o.toURIFragment());
+  }
 
-    if (obj != null && obj.getClass() == getClass())
-    {
-      CDOIDObjectLongWithClassifierImpl that = (CDOIDObjectLongWithClassifierImpl)obj;
-      return ObjectUtil.equals(classifierRef, that.classifierRef) && getLongValue() == that.getLongValue();
-    }
+  private Object readResolve() throws ObjectStreamException
+  {
+    return create(value, classifierRef);
+  }
 
-    return false;
+  private static int getHashCode(long value, CDOClassifierRef classifierRef)
+  {
+    return ObjectUtil.hashCode(value) ^ classifierRef.hashCode();
   }
 
-  @Override
-  public int hashCode()
+  public static CDOIDObjectLongWithClassifierImpl create(long value, CDOClassifierRef classifierRef)
   {
-    int hashCode = classifierRef.hashCode() ^ ObjectUtil.hashCode(getLongValue());
-    return getClass().hashCode() ^ hashCode;
+    return INTERNER.intern(value, classifierRef);
   }
 
-  @Override
-  public String toString()
+  public static CDOIDObjectLongWithClassifierImpl create(CDODataInput in) throws IOException
   {
-    return "OID:" + toURIFragment(); //$NON-NLS-1$
+    long value = in.readLong();
+    CDOClassifierRef classifierRef = in.readCDOClassifierRef();
+    return create(value, classifierRef);
   }
 
-  @Override
-  protected int doCompareTo(CDOID o) throws ClassCastException
+  public static CDOIDObjectLongWithClassifierImpl create(String fragmentPart)
   {
-    // conversion to uri fragment is pretty heavy but afaics the compareTo
-    // is not used in a critical place.
-    return toURIFragment().compareTo(o.toURIFragment());
+    int index1 = fragmentPart.indexOf(CDOClassifierRef.URI_SEPARATOR);
+    int index2 = fragmentPart.indexOf(CDOClassifierRef.URI_SEPARATOR, index1 + 1);
+    if (index1 == -1 || index2 == -1)
+    {
+      throw new IllegalArgumentException("The fragment " + fragmentPart + " is not a valid fragment");
+    }
+
+    String packageURI = fragmentPart.substring(0, index1);
+    String classifierName = fragmentPart.substring(index1 + 1, index2);
+    CDOClassifierRef classifierRef = new CDOClassifierRef(packageURI, classifierName);
+
+    long value = Long.parseLong(fragmentPart.substring(index2 + 1));
+    return create(value, classifierRef);
+  }
+
+  /**
+   * @author Eike Stepper
+   */
+  private static final class LongWithClassifierInterner extends Interner<CDOIDObjectLongWithClassifierImpl>
+  {
+    public synchronized CDOIDObjectLongWithClassifierImpl intern(long value, CDOClassifierRef classifierRef)
+    {
+      int hashCode = getHashCode(value, classifierRef);
+      for (Entry<CDOIDObjectLongWithClassifierImpl> entry = getEntry(hashCode); entry != null; entry = entry
+          .getNextEntry())
+      {
+        CDOIDObjectLongWithClassifierImpl id = entry.get();
+        if (id != null && id.value == value && id.classifierRef.equals(classifierRef))
+        {
+          return id;
+        }
+      }
+
+      CDOIDObjectLongWithClassifierImpl id = new CDOIDObjectLongWithClassifierImpl(value, classifierRef);
+      addEntry(createEntry(id, hashCode));
+      return id;
+    }
+
+    @Override
+    protected int hashCode(CDOIDObjectLongWithClassifierImpl id)
+    {
+      return getHashCode(id.value, id.classifierRef);
+    }
   }
 }
diff --git a/plugins/org.eclipse.emf.cdo.common/src/org/eclipse/emf/cdo/internal/common/id/CDOIDObjectStringImpl.java b/plugins/org.eclipse.emf.cdo.common/src/org/eclipse/emf/cdo/internal/common/id/CDOIDObjectStringImpl.java
index 376a113b81..12cce04f7d 100644
--- a/plugins/org.eclipse.emf.cdo.common/src/org/eclipse/emf/cdo/internal/common/id/CDOIDObjectStringImpl.java
+++ b/plugins/org.eclipse.emf.cdo.common/src/org/eclipse/emf/cdo/internal/common/id/CDOIDObjectStringImpl.java
@@ -6,48 +6,68 @@
  * http://www.eclipse.org/legal/epl-v10.html
  *
  * Contributors:
- *    Martin Taal - initial API and implementation
- *    Eike Stepper - maintenance
+ *    Eike Stepper - initial API and implementation
  */
 package org.eclipse.emf.cdo.internal.common.id;
 
 import org.eclipse.emf.cdo.common.id.CDOID;
-import org.eclipse.emf.cdo.spi.common.id.AbstractCDOIDString;
+import org.eclipse.emf.cdo.common.id.CDOIDString;
+import org.eclipse.emf.cdo.common.protocol.CDODataInput;
+import org.eclipse.emf.cdo.common.protocol.CDODataOutput;
+import org.eclipse.emf.cdo.spi.common.id.AbstractCDOID;
 import org.eclipse.emf.cdo.spi.common.id.InternalCDOIDObject;
 
+import org.eclipse.net4j.util.CheckUtil;
+import org.eclipse.net4j.util.ref.Interner;
+
+import java.io.IOException;
+import java.io.ObjectStreamException;
+
 /**
- * @author Martin Taal
- * @since 3.0
+ * @author Eike Stepper
+ * @since 2.0
  */
-public class CDOIDObjectStringImpl extends AbstractCDOIDString implements InternalCDOIDObject
+public final class CDOIDObjectStringImpl extends AbstractCDOID implements InternalCDOIDObject, CDOIDString
 {
   private static final long serialVersionUID = 1L;
 
-  public CDOIDObjectStringImpl()
+  private static final StringInterner INTERNER = new StringInterner();
+
+  private final String value;
+
+  private CDOIDObjectStringImpl(String value)
   {
+    CheckUtil.checkArg(value, "Null not allowed");
+    this.value = value;
   }
 
-  public CDOIDObjectStringImpl(String value)
+  @Override
+  public void write(CDODataOutput out) throws IOException
   {
-    super(value);
+    out.writeString(value);
   }
 
-  public Type getType()
+  public String toURIFragment()
   {
-    return Type.OBJECT;
+    return value;
   }
 
-  public boolean isDangling()
+  public String getStringValue()
   {
-    return false;
+    return value;
   }
 
-  public boolean isExternal()
+  public Type getType()
   {
-    return false;
+    return Type.OBJECT;
   }
 
-  public boolean isNull()
+  public CDOID.ObjectType getSubType()
+  {
+    return CDOID.ObjectType.STRING;
+  }
+
+  public boolean isExternal()
   {
     return false;
   }
@@ -62,20 +82,71 @@ public class CDOIDObjectStringImpl extends AbstractCDOIDString implements Intern
     return false;
   }
 
-  public CDOID.ObjectType getSubType()
+  @Override
+  public int hashCode()
   {
-    return CDOID.ObjectType.STRING;
+    return value.hashCode();
   }
 
   @Override
   public String toString()
   {
-    return "OID" + getStringValue(); //$NON-NLS-1$
+    return "OID" + value; //$NON-NLS-1$
   }
 
   @Override
   protected int doCompareTo(CDOID o) throws ClassCastException
   {
-    return getStringValue().compareTo(((CDOIDObjectStringImpl)o).getStringValue());
+    return value.compareTo(((CDOIDObjectStringImpl)o).value);
+  }
+
+  private Object readResolve() throws ObjectStreamException
+  {
+    return create(value);
+  }
+
+  private static int getHashCode(String value)
+  {
+    return value.hashCode();
+  }
+
+  public static CDOIDObjectStringImpl create(String value)
+  {
+    return INTERNER.intern(value);
+  }
+
+  public static CDOIDObjectStringImpl create(CDODataInput in) throws IOException
+  {
+    String value = in.readString();
+    return create(value);
+  }
+
+  /**
+   * @author Eike Stepper
+   */
+  private static final class StringInterner extends Interner<CDOIDObjectStringImpl>
+  {
+    public synchronized CDOIDObjectStringImpl intern(String value)
+    {
+      int hashCode = getHashCode(value);
+      for (Entry<CDOIDObjectStringImpl> entry = getEntry(hashCode); entry != null; entry = entry.getNextEntry())
+      {
+        CDOIDObjectStringImpl id = entry.get();
+        if (id != null && id.value.equals(value))
+        {
+          return id;
+        }
+      }
+
+      CDOIDObjectStringImpl id = new CDOIDObjectStringImpl(value);
+      addEntry(createEntry(id, hashCode));
+      return id;
+    }
+
+    @Override
+    protected int hashCode(CDOIDObjectStringImpl id)
+    {
+      return getHashCode(id.value);
+    }
   }
 }
diff --git a/plugins/org.eclipse.emf.cdo.common/src/org/eclipse/emf/cdo/internal/common/id/CDOIDObjectStringWithClassifierImpl.java b/plugins/org.eclipse.emf.cdo.common/src/org/eclipse/emf/cdo/internal/common/id/CDOIDObjectStringWithClassifierImpl.java
index 6b6ed62ff2..f032d53dcb 100644
--- a/plugins/org.eclipse.emf.cdo.common/src/org/eclipse/emf/cdo/internal/common/id/CDOIDObjectStringWithClassifierImpl.java
+++ b/plugins/org.eclipse.emf.cdo.common/src/org/eclipse/emf/cdo/internal/common/id/CDOIDObjectStringWithClassifierImpl.java
@@ -12,34 +12,44 @@
 package org.eclipse.emf.cdo.internal.common.id;
 
 import org.eclipse.emf.cdo.common.id.CDOID;
+import org.eclipse.emf.cdo.common.id.CDOIDString;
 import org.eclipse.emf.cdo.common.model.CDOClassifierRef;
 import org.eclipse.emf.cdo.common.protocol.CDODataInput;
 import org.eclipse.emf.cdo.common.protocol.CDODataOutput;
+import org.eclipse.emf.cdo.spi.common.id.AbstractCDOID;
+import org.eclipse.emf.cdo.spi.common.id.InternalCDOIDObject;
 
-import org.eclipse.net4j.util.ObjectUtil;
-import org.eclipse.net4j.util.io.ExtendedDataInput;
-import org.eclipse.net4j.util.io.ExtendedDataOutput;
+import org.eclipse.net4j.util.CheckUtil;
+import org.eclipse.net4j.util.ref.Interner;
 
 import java.io.IOException;
+import java.io.ObjectStreamException;
 
 /**
  * @author Martin Taal
  * @since 3.0
  */
-public class CDOIDObjectStringWithClassifierImpl extends CDOIDObjectStringImpl implements CDOClassifierRef.Provider
+public final class CDOIDObjectStringWithClassifierImpl extends AbstractCDOID implements InternalCDOIDObject,
+    CDOIDString, CDOClassifierRef.Provider
 {
   private static final long serialVersionUID = 1L;
 
-  private CDOClassifierRef classifierRef;
+  private static final StringWithClassifierInterner INTERNER = new StringWithClassifierInterner();
 
-  public CDOIDObjectStringWithClassifierImpl()
+  private final String value;
+
+  private final CDOClassifierRef classifierRef;
+
+  private CDOIDObjectStringWithClassifierImpl(String value, CDOClassifierRef classifierRef)
   {
+    CheckUtil.checkArg(value, "Null not allowed");
+    this.value = value;
+    this.classifierRef = classifierRef;
   }
 
-  public CDOIDObjectStringWithClassifierImpl(CDOClassifierRef classifierRef, String value)
+  public String getStringValue()
   {
-    super(value);
-    this.classifierRef = classifierRef;
+    return value;
   }
 
   public CDOClassifierRef getClassifierRef()
@@ -48,78 +58,47 @@ public class CDOIDObjectStringWithClassifierImpl extends CDOIDObjectStringImpl i
   }
 
   @Override
-  public CDOID.ObjectType getSubType()
+  public void write(CDODataOutput out) throws IOException
   {
-    return CDOID.ObjectType.STRING_WITH_CLASSIFIER;
+    out.writeString(value);
+    out.writeCDOClassifierRef(classifierRef);
   }
 
-  @Override
   public String toURIFragment()
   {
-    return getClassifierRef().getPackageURI() + CDOClassifierRef.URI_SEPARATOR + getClassifierRef().getClassifierName()
-        + CDOClassifierRef.URI_SEPARATOR + super.toURIFragment();
+    return classifierRef.getPackageURI() + CDOClassifierRef.URI_SEPARATOR + classifierRef.getClassifierName()
+        + CDOClassifierRef.URI_SEPARATOR + value;
   }
 
-  @Override
-  public void read(String fragmentPart)
+  public Type getType()
   {
-    // get the EClass part
-    int index1 = fragmentPart.indexOf(CDOClassifierRef.URI_SEPARATOR);
-    int index2 = fragmentPart.indexOf(CDOClassifierRef.URI_SEPARATOR, index1 + 1);
-    if (index1 == -1 || index2 == -1)
-    {
-      throw new IllegalArgumentException("The fragment " + fragmentPart + " is invalid");
-    }
-
-    classifierRef = new CDOClassifierRef(fragmentPart.substring(0, index1), fragmentPart.substring(index1 + 1, index2));
-
-    // let the super take care of the rest
-    super.read(fragmentPart.substring(index2 + 1));
+    return Type.OBJECT;
   }
 
-  @Override
-  public void read(ExtendedDataInput in) throws IOException
+  public CDOID.ObjectType getSubType()
   {
-    CDODataInput cdoDataInput = (CDODataInput)in;
-    classifierRef = cdoDataInput.readCDOClassifierRef();
-
-    // and let the super take care of the rest
-    super.read(in);
+    return CDOID.ObjectType.STRING_WITH_CLASSIFIER;
   }
 
-  @Override
-  public void write(ExtendedDataOutput out) throws IOException
+  public boolean isExternal()
   {
-    // TODO: change the parameter to prevent casting to CDODataInput
-    CDODataOutput cdoDataOutput = (CDODataOutput)out;
-    cdoDataOutput.writeCDOClassifierRef(classifierRef);
-
-    // and let the super write the rest
-    super.write(out);
+    return false;
   }
 
-  @Override
-  public boolean equals(Object obj)
+  public boolean isObject()
   {
-    if (obj == this)
-    {
-      return true;
-    }
-
-    if (obj != null && obj.getClass() == getClass())
-    {
-      CDOIDObjectStringWithClassifierImpl that = (CDOIDObjectStringWithClassifierImpl)obj;
-      return ObjectUtil.equals(classifierRef, that.classifierRef) && getStringValue().equals(that.getStringValue());
-    }
+    return true;
+  }
 
+  public boolean isTemporary()
+  {
     return false;
   }
 
   @Override
   public int hashCode()
   {
-    int hashCode = classifierRef.hashCode() ^ ObjectUtil.hashCode(getStringValue());
-    return getClass().hashCode() ^ hashCode;
+    return getHashCode(value, classifierRef);
   }
 
   @Override
@@ -131,8 +110,75 @@ public class CDOIDObjectStringWithClassifierImpl extends CDOIDObjectStringImpl i
   @Override
   protected int doCompareTo(CDOID o) throws ClassCastException
   {
-    // conversion to uri fragment is pretty heavy but afaics the compareTo
-    // is not used in a critical place.
     return toURIFragment().compareTo(o.toURIFragment());
   }
+
+  private Object readResolve() throws ObjectStreamException
+  {
+    return create(value, classifierRef);
+  }
+
+  private static int getHashCode(String value, CDOClassifierRef classifierRef)
+  {
+    return value.hashCode() ^ classifierRef.hashCode();
+  }
+
+  public static CDOIDObjectStringWithClassifierImpl create(String value, CDOClassifierRef classifierRef)
+  {
+    return INTERNER.intern(value, classifierRef);
+  }
+
+  public static CDOIDObjectStringWithClassifierImpl create(CDODataInput in) throws IOException
+  {
+    String value = in.readString();
+    CDOClassifierRef classifierRef = in.readCDOClassifierRef();
+    return create(value, classifierRef);
+  }
+
+  public static CDOIDObjectStringWithClassifierImpl create(String fragmentPart)
+  {
+    int index1 = fragmentPart.indexOf(CDOClassifierRef.URI_SEPARATOR);
+    int index2 = fragmentPart.indexOf(CDOClassifierRef.URI_SEPARATOR, index1 + 1);
+    if (index1 == -1 || index2 == -1)
+    {
+      throw new IllegalArgumentException("The fragment " + fragmentPart + " is invalid");
+    }
+
+    String packageURI = fragmentPart.substring(0, index1);
+    String classifierName = fragmentPart.substring(index1 + 1, index2);
+    CDOClassifierRef classifierRef = new CDOClassifierRef(packageURI, classifierName);
+
+    String value = fragmentPart.substring(index2 + 1);
+    return create(value, classifierRef);
+  }
+
+  /**
+   * @author Eike Stepper
+   */
+  private static final class StringWithClassifierInterner extends Interner<CDOIDObjectStringWithClassifierImpl>
+  {
+    public synchronized CDOIDObjectStringWithClassifierImpl intern(String value, CDOClassifierRef classifierRef)
+    {
+      int hashCode = getHashCode(value, classifierRef);
+      for (Entry<CDOIDObjectStringWithClassifierImpl> entry = getEntry(hashCode); entry != null; entry = entry
+          .getNextEntry())
+      {
+        CDOIDObjectStringWithClassifierImpl id = entry.get();
+        if (id != null && id.value.equals(value) && id.classifierRef.equals(classifierRef))
+        {
+          return id;
+        }
+      }
+
+      CDOIDObjectStringWithClassifierImpl id = new CDOIDObjectStringWithClassifierImpl(value, classifierRef);
+      addEntry(createEntry(id, hashCode));
+      return id;
+    }
+
+    @Override
+    protected int hashCode(CDOIDObjectStringWithClassifierImpl id)
+    {
+      return getHashCode(id.value, id.classifierRef);
+    }
+  }
 }
diff --git a/plugins/org.eclipse.emf.cdo.common/src/org/eclipse/emf/cdo/internal/common/id/CDOIDObjectUUIDImpl.java b/plugins/org.eclipse.emf.cdo.common/src/org/eclipse/emf/cdo/internal/common/id/CDOIDObjectUUIDImpl.java
index fd76f4f4b4..70ca6411b5 100644
--- a/plugins/org.eclipse.emf.cdo.common/src/org/eclipse/emf/cdo/internal/common/id/CDOIDObjectUUIDImpl.java
+++ b/plugins/org.eclipse.emf.cdo.common/src/org/eclipse/emf/cdo/internal/common/id/CDOIDObjectUUIDImpl.java
@@ -12,42 +12,64 @@
 package org.eclipse.emf.cdo.internal.common.id;
 
 import org.eclipse.emf.cdo.common.id.CDOID;
-import org.eclipse.emf.cdo.spi.common.id.AbstractCDOIDByteArray;
+import org.eclipse.emf.cdo.common.id.CDOIDUtil;
+import org.eclipse.emf.cdo.common.protocol.CDODataInput;
+import org.eclipse.emf.cdo.common.protocol.CDODataOutput;
+import org.eclipse.emf.cdo.spi.common.id.AbstractCDOID;
 import org.eclipse.emf.cdo.spi.common.id.InternalCDOIDObject;
 
+import org.eclipse.net4j.util.CheckUtil;
+import org.eclipse.net4j.util.ref.Interner;
+
+import java.io.IOException;
+import java.io.ObjectStreamException;
+import java.util.Arrays;
+
 /**
  * @author Martin Taal
  * @since 3.0
  */
-public class CDOIDObjectUUIDImpl extends AbstractCDOIDByteArray implements InternalCDOIDObject
+public final class CDOIDObjectUUIDImpl extends AbstractCDOID implements InternalCDOIDObject
 {
   private static final long serialVersionUID = 1L;
 
-  public CDOIDObjectUUIDImpl()
+  private static final UUIDInterner INTERNER = new UUIDInterner();
+
+  private final byte[] value;
+
+  private CDOIDObjectUUIDImpl(byte[] value)
   {
+    CheckUtil.checkArg(value, "Null not allowed");
+    this.value = value;
   }
 
-  public CDOIDObjectUUIDImpl(byte[] value)
+  public byte[] getByteArrayValue()
   {
-    super(value);
+    return value;
   }
 
-  public Type getType()
+  @Override
+  public void write(CDODataOutput out) throws IOException
   {
-    return Type.OBJECT;
+    out.writeByteArray(value);
   }
 
-  public boolean isDangling()
+  public String toURIFragment()
   {
-    return false;
+    return CDOIDUtil.encodeUUID(value);
   }
 
-  public boolean isExternal()
+  public Type getType()
   {
-    return false;
+    return Type.OBJECT;
   }
 
-  public boolean isNull()
+  public CDOID.ObjectType getSubType()
+  {
+    return CDOID.ObjectType.UUID;
+  }
+
+  public boolean isExternal()
   {
     return false;
   }
@@ -62,21 +84,21 @@ public class CDOIDObjectUUIDImpl extends AbstractCDOIDByteArray implements Inter
     return false;
   }
 
-  public CDOID.ObjectType getSubType()
+  @Override
+  public int hashCode()
   {
-    return CDOID.ObjectType.UUID;
+    return getHashCode(value);
   }
 
   @Override
   protected int doCompareTo(CDOID o) throws ClassCastException
   {
-    byte[] thisValue = getByteArrayValue();
-    byte[] thatValue = ((CDOIDObjectUUIDImpl)o).getByteArrayValue();
-    int minLength = Math.min(thisValue.length, thatValue.length);
+    byte[] thatValue = ((CDOIDObjectUUIDImpl)o).value;
+    int minLength = Math.min(value.length, thatValue.length);
 
     for (int i = 0; i < minLength; i++)
     {
-      byte thisByte = thisValue[i];
+      byte thisByte = value[i];
       byte thatByte = thatValue[i];
       if (thisByte < thatByte)
       {
@@ -89,16 +111,72 @@ public class CDOIDObjectUUIDImpl extends AbstractCDOIDByteArray implements Inter
       }
     }
 
-    if (thisValue.length < thatValue.length)
+    if (value.length < thatValue.length)
     {
       return -1;
     }
 
-    if (thisValue.length > thatValue.length)
+    if (value.length > thatValue.length)
     {
       return 1;
     }
 
     return 0;
   }
+
+  private Object readResolve() throws ObjectStreamException
+  {
+    return create(value);
+  }
+
+  private static int getHashCode(byte[] value)
+  {
+    return Arrays.hashCode(value);
+  }
+
+  public static CDOIDObjectUUIDImpl create(byte[] value)
+  {
+    return INTERNER.intern(value);
+  }
+
+  public static CDOIDObjectUUIDImpl create(CDODataInput in) throws IOException
+  {
+    byte[] value = in.readByteArray();
+    return create(value);
+  }
+
+  public static CDOIDObjectUUIDImpl create(String fragmentPart)
+  {
+    byte[] value = CDOIDUtil.decodeUUID(fragmentPart);
+    return create(value);
+  }
+
+  /**
+   * @author Eike Stepper
+   */
+  private static final class UUIDInterner extends Interner<CDOIDObjectUUIDImpl>
+  {
+    public synchronized CDOIDObjectUUIDImpl intern(byte[] value)
+    {
+      int hashCode = getHashCode(value);
+      for (Entry<CDOIDObjectUUIDImpl> entry = getEntry(hashCode); entry != null; entry = entry.getNextEntry())
+      {
+        CDOIDObjectUUIDImpl id = entry.get();
+        if (id != null && Arrays.equals(id.value, value))
+        {
+          return id;
+        }
+      }
+
+      CDOIDObjectUUIDImpl id = new CDOIDObjectUUIDImpl(value);
+      addEntry(createEntry(id, hashCode));
+      return id;
+    }
+
+    @Override
+    protected int hashCode(CDOIDObjectUUIDImpl id)
+    {
+      return getHashCode(id.value);
+    }
+  }
 }
diff --git a/plugins/org.eclipse.emf.cdo.common/src/org/eclipse/emf/cdo/internal/common/id/CDOIDTempObjectExternalImpl.java b/plugins/org.eclipse.emf.cdo.common/src/org/eclipse/emf/cdo/internal/common/id/CDOIDTempObjectExternalImpl.java
index b72babdd7e..ac1cb3a843 100644
--- a/plugins/org.eclipse.emf.cdo.common/src/org/eclipse/emf/cdo/internal/common/id/CDOIDTempObjectExternalImpl.java
+++ b/plugins/org.eclipse.emf.cdo.common/src/org/eclipse/emf/cdo/internal/common/id/CDOIDTempObjectExternalImpl.java
@@ -4,30 +4,150 @@
  * are made available under the terms of the Eclipse Public License v1.0
  * which accompanies this distribution, and is available at
  * http://www.eclipse.org/legal/epl-v10.html
- * 
+ *
  * Contributors:
- *    Simon McDuff - initial API and implementation
- *    Eike Stepper - maintenance
+ *    Eike Stepper - initial API and implementation
  */
 package org.eclipse.emf.cdo.internal.common.id;
 
+import org.eclipse.emf.cdo.common.id.CDOID;
+import org.eclipse.emf.cdo.common.id.CDOIDExternal;
+import org.eclipse.emf.cdo.common.id.CDOIDString;
 import org.eclipse.emf.cdo.common.id.CDOIDTemp;
+import org.eclipse.emf.cdo.common.protocol.CDODataInput;
+import org.eclipse.emf.cdo.common.protocol.CDODataOutput;
+import org.eclipse.emf.cdo.spi.common.id.AbstractCDOID;
+
+import org.eclipse.net4j.util.CheckUtil;
+import org.eclipse.net4j.util.ref.Interner;
+
+import java.io.IOException;
+import java.io.ObjectStreamException;
 
 /**
- * @author Simon McDuff
+ * @author Eike Stepper
+ * @since 2.0
  */
-public class CDOIDTempObjectExternalImpl extends CDOIDExternalImpl implements CDOIDTemp
+public final class CDOIDTempObjectExternalImpl extends AbstractCDOID implements CDOIDExternal, CDOIDTemp, CDOIDString
 {
   private static final long serialVersionUID = 1L;
 
-  public CDOIDTempObjectExternalImpl(String uri)
+  private static final StringInterner INTERNER = new StringInterner();
+
+  private final String uri;
+
+  private CDOIDTempObjectExternalImpl(String uri)
   {
-    super(uri);
+    CheckUtil.checkArg(uri, "Null not allowed");
+    this.uri = uri;
   }
 
   @Override
+  public void write(CDODataOutput out) throws IOException
+  {
+    out.writeString(uri);
+  }
+
+  public String toURIFragment()
+  {
+    return uri;
+  }
+
+  public String getURI()
+  {
+    return uri;
+  }
+
+  public String getStringValue()
+  {
+    return uri;
+  }
+
   public Type getType()
   {
     return Type.EXTERNAL_TEMP_OBJECT;
   }
+
+  public boolean isExternal()
+  {
+    return true;
+  }
+
+  public boolean isObject()
+  {
+    return true;
+  }
+
+  public boolean isTemporary()
+  {
+    return true;
+  }
+
+  @Override
+  public int hashCode()
+  {
+    return uri.hashCode();
+  }
+
+  @Override
+  public String toString()
+  {
+    return "oid:" + uri; //$NON-NLS-1$
+  }
+
+  @Override
+  protected int doCompareTo(CDOID o) throws ClassCastException
+  {
+    return uri.compareTo(((CDOIDTempObjectExternalImpl)o).uri);
+  }
+
+  private Object readResolve() throws ObjectStreamException
+  {
+    return create(uri);
+  }
+
+  private static int getHashCode(String uri)
+  {
+    return uri.hashCode();
+  }
+
+  public static CDOIDTempObjectExternalImpl create(String uri)
+  {
+    return INTERNER.intern(uri);
+  }
+
+  public static CDOIDTempObjectExternalImpl create(CDODataInput in) throws IOException
+  {
+    String uri = in.readString();
+    return create(uri);
+  }
+
+  /**
+   * @author Eike Stepper
+   */
+  private static final class StringInterner extends Interner<CDOIDTempObjectExternalImpl>
+  {
+    public synchronized CDOIDTempObjectExternalImpl intern(String uri)
+    {
+      int hashCode = getHashCode(uri);
+      for (Entry<CDOIDTempObjectExternalImpl> entry = getEntry(hashCode); entry != null; entry = entry.getNextEntry())
+      {
+        CDOIDTempObjectExternalImpl id = entry.get();
+        if (id != null && id.uri.equals(uri))
+        {
+          return id;
+        }
+      }
+
+      CDOIDTempObjectExternalImpl id = new CDOIDTempObjectExternalImpl(uri);
+      addEntry(createEntry(id, hashCode));
+      return id;
+    }
+
+    @Override
+    protected int hashCode(CDOIDTempObjectExternalImpl id)
+    {
+      return getHashCode(id.uri);
+    }
+  }
 }
diff --git a/plugins/org.eclipse.emf.cdo.common/src/org/eclipse/emf/cdo/internal/common/id/CDOIDTempObjectImpl.java b/plugins/org.eclipse.emf.cdo.common/src/org/eclipse/emf/cdo/internal/common/id/CDOIDTempObjectImpl.java
index 2cc4034065..54232a02da 100644
--- a/plugins/org.eclipse.emf.cdo.common/src/org/eclipse/emf/cdo/internal/common/id/CDOIDTempObjectImpl.java
+++ b/plugins/org.eclipse.emf.cdo.common/src/org/eclipse/emf/cdo/internal/common/id/CDOIDTempObjectImpl.java
@@ -12,36 +12,56 @@ package org.eclipse.emf.cdo.internal.common.id;
 
 import org.eclipse.emf.cdo.common.id.CDOID;
 import org.eclipse.emf.cdo.common.id.CDOIDTemp;
-import org.eclipse.emf.cdo.spi.common.id.AbstractCDOIDInteger;
+import org.eclipse.emf.cdo.common.protocol.CDODataInput;
+import org.eclipse.emf.cdo.common.protocol.CDODataOutput;
+import org.eclipse.emf.cdo.spi.common.id.AbstractCDOID;
+
+import org.eclipse.net4j.util.CheckUtil;
+import org.eclipse.net4j.util.ObjectUtil;
+import org.eclipse.net4j.util.ref.Interner;
+
+import java.io.IOException;
 
 /**
  * @author Eike Stepper
+ * @since 2.0
  */
-public class CDOIDTempObjectImpl extends AbstractCDOIDInteger implements CDOIDTemp
+public final class CDOIDTempObjectImpl extends AbstractCDOID implements CDOIDTemp
 {
   private static final long serialVersionUID = 1L;
 
-  public CDOIDTempObjectImpl(int value)
+  private static final IntInterner INTERNER = new IntInterner();
+
+  private final int value;
+
+  private CDOIDTempObjectImpl(int value)
   {
-    super(value);
+    CheckUtil.checkArg(value != 0, "Zero not allowed");
+    this.value = value;
   }
 
-  public Type getType()
+  public int getIntValue()
   {
-    return Type.TEMP_OBJECT;
+    return value;
   }
 
-  public boolean isDangling()
+  @Override
+  public void write(CDODataOutput out) throws IOException
   {
-    return false;
+    out.writeInt(value);
   }
 
-  public boolean isExternal()
+  public String toURIFragment()
   {
-    return false;
+    return String.valueOf(value);
   }
 
-  public boolean isNull()
+  public Type getType()
+  {
+    return Type.TEMP_OBJECT;
+  }
+
+  public boolean isExternal()
   {
     return false;
   }
@@ -57,14 +77,82 @@ public class CDOIDTempObjectImpl extends AbstractCDOIDInteger implements CDOIDTe
   }
 
   @Override
+  public int hashCode()
+  {
+    return ObjectUtil.hashCode(value);
+  }
+
+  @Override
   public String toString()
   {
-    return "oid" + getIntValue(); //$NON-NLS-1$
+    return "oid" + value; //$NON-NLS-1$
   }
 
   @Override
   protected int doCompareTo(CDOID o) throws ClassCastException
   {
-    return new Integer(getIntValue()).compareTo(((CDOIDTempObjectImpl)o).getIntValue());
+    CDOIDTempObjectImpl that = (CDOIDTempObjectImpl)o;
+    if (value < that.value)
+    {
+      return -1;
+    }
+
+    if (value > that.value)
+    {
+      return 1;
+    }
+
+    return 0;
+  }
+
+  private static int getHashCode(int value)
+  {
+    return value;
+  }
+
+  public static CDOIDTempObjectImpl create(int value)
+  {
+    return INTERNER.intern(value);
+  }
+
+  public static CDOIDTempObjectImpl create(CDODataInput in) throws IOException
+  {
+    int value = in.readInt();
+    return create(value);
+  }
+
+  public static CDOIDTempObjectImpl create(String fragmentPart)
+  {
+    int value = Integer.parseInt(fragmentPart);
+    return create(value);
+  }
+
+  /**
+   * @author Eike Stepper
+   */
+  private static final class IntInterner extends Interner<CDOIDTempObjectImpl>
+  {
+    public synchronized CDOIDTempObjectImpl intern(int value)
+    {
+      int hashCode = getHashCode(value);
+      for (Entry<CDOIDTempObjectImpl> entry = getEntry(hashCode); entry != null; entry = entry.getNextEntry())
+      {
+        CDOIDTempObjectImpl id = entry.get();
+        if (id != null && id.value == value)
+        {
+          return id;
+        }
+      }
+
+      CDOIDTempObjectImpl id = new CDOIDTempObjectImpl(value);
+      addEntry(createEntry(id, hashCode));
+      return id;
+    }
+
+    @Override
+    protected int hashCode(CDOIDTempObjectImpl id)
+    {
+      return getHashCode(id.value);
+    }
   }
 }
diff --git a/plugins/org.eclipse.emf.cdo.common/src/org/eclipse/emf/cdo/spi/common/id/AbstractCDOID.java b/plugins/org.eclipse.emf.cdo.common/src/org/eclipse/emf/cdo/spi/common/id/AbstractCDOID.java
index fff20d46dc..dba32b576c 100644
--- a/plugins/org.eclipse.emf.cdo.common/src/org/eclipse/emf/cdo/spi/common/id/AbstractCDOID.java
+++ b/plugins/org.eclipse.emf.cdo.common/src/org/eclipse/emf/cdo/spi/common/id/AbstractCDOID.java
@@ -12,6 +12,7 @@
 package org.eclipse.emf.cdo.spi.common.id;
 
 import org.eclipse.emf.cdo.common.id.CDOID;
+import org.eclipse.emf.cdo.common.protocol.CDODataOutput;
 
 import org.eclipse.net4j.util.io.ExtendedDataInput;
 import org.eclipse.net4j.util.io.ExtendedDataOutput;
@@ -29,10 +30,59 @@ public abstract class AbstractCDOID implements CDOID
 {
   private static final long serialVersionUID = 1L;
 
-  public AbstractCDOID()
+  protected AbstractCDOID()
   {
   }
 
+  /**
+   * @since 4.2
+   */
+  public boolean isNull()
+  {
+    return false;
+  }
+
+  /**
+   * @since 4.2
+   */
+  @Deprecated
+  public final boolean isDangling()
+  {
+    return false;
+  }
+
+  /**
+   * @deprecated As of 4.2 not called anymore.
+   */
+  @Deprecated
+  public final void read(String fragmentPart)
+  {
+    // Do nothing
+  }
+
+  /**
+   * @deprecated As of 4.2 not called anymore.
+   */
+  @Deprecated
+  public final void read(ExtendedDataInput in) throws IOException
+  {
+    // Do nothing
+  }
+
+  /**
+   * @deprecated As of 4.2 {@link #write(CDODataOutput)} is called.
+   */
+  @Deprecated
+  public void write(ExtendedDataOutput out) throws IOException
+  {
+    // Do nothing
+  }
+
+  /**
+   * @since 4.2
+   */
+  public abstract void write(CDODataOutput out) throws IOException;
+
   @Override
   public String toString()
   {
@@ -51,20 +101,14 @@ public abstract class AbstractCDOID implements CDOID
     }
   }
 
-  protected abstract int doCompareTo(CDOID o) throws ClassCastException;
-
-  /**
-   * <b>Note:</b> {@link CDOID#toURIFragment()} and {@link AbstractCDOID#read(String)} need to match.
-   */
-  public abstract void read(String fragmentPart);
+  @Override
+  public boolean equals(Object obj)
+  {
+    return obj == this;
+  }
 
-  /**
-   * TODO: Change the parameter to CDODataInput to prevent casting in IDs with classifier.
-   */
-  public abstract void read(ExtendedDataInput in) throws IOException;
+  @Override
+  public abstract int hashCode();
 
-  /**
-   * TODO: Change the parameter to CDODataInput to prevent casting in IDs with classifier.
-   */
-  public abstract void write(ExtendedDataOutput out) throws IOException;
+  protected abstract int doCompareTo(CDOID o) throws ClassCastException;
 }
diff --git a/plugins/org.eclipse.emf.cdo.common/src/org/eclipse/emf/cdo/spi/common/id/AbstractCDOIDByteArray.java b/plugins/org.eclipse.emf.cdo.common/src/org/eclipse/emf/cdo/spi/common/id/AbstractCDOIDByteArray.java
deleted file mode 100644
index e51369a1e3..0000000000
--- a/plugins/org.eclipse.emf.cdo.common/src/org/eclipse/emf/cdo/spi/common/id/AbstractCDOIDByteArray.java
+++ /dev/null
@@ -1,97 +0,0 @@
-/*
- * Copyright (c) 2004 - 2012 Eike Stepper (Berlin, Germany) and others.
- * All rights reserved. This program and the accompanying materials
- * are made available under the terms of the Eclipse Public License v1.0
- * which accompanies this distribution, and is available at
- * http://www.eclipse.org/legal/epl-v10.html
- *
- * Contributors:
- *    Eike Stepper - initial API and implementation
- */
-package org.eclipse.emf.cdo.spi.common.id;
-
-import org.eclipse.emf.cdo.common.id.CDOIDUtil;
-
-import org.eclipse.net4j.util.CheckUtil;
-import org.eclipse.net4j.util.io.ExtendedDataInput;
-import org.eclipse.net4j.util.io.ExtendedDataOutput;
-
-import java.io.IOException;
-import java.util.Arrays;
-
-/**
- * If the meaning of this type isn't clear, there really should be more of a description here...
- *
- * @author Eike Stepper
- * @since 4.1
- * @noextend This interface is not intended to be extended by clients.
- */
-public abstract class AbstractCDOIDByteArray extends AbstractCDOID
-{
-  public static final String NULL_VALUE = null;
-
-  private static final long serialVersionUID = 1L;
-
-  private byte[] value;
-
-  public AbstractCDOIDByteArray()
-  {
-  }
-
-  public AbstractCDOIDByteArray(byte[] value)
-  {
-    CheckUtil.checkArg(value != null && value.length == 16, "Illegal UUID value");
-    this.value = value;
-  }
-
-  public byte[] getByteArrayValue()
-  {
-    return value;
-  }
-
-  public String toURIFragment()
-  {
-    return CDOIDUtil.encodeUUID(value);
-  }
-
-  @Override
-  public void read(String fragmentPart)
-  {
-    value = CDOIDUtil.decodeUUID(fragmentPart);
-  }
-
-  @Override
-  public void read(ExtendedDataInput in) throws IOException
-  {
-    value = in.readByteArray();
-  }
-
-  @Override
-  public void write(ExtendedDataOutput out) throws IOException
-  {
-    out.writeByteArray(value);
-  }
-
-  @Override
-  public boolean equals(Object obj)
-  {
-    if (obj == this)
-    {
-      return true;
-    }
-
-    if (obj != null && obj.getClass() == getClass())
-    {
-      AbstractCDOIDByteArray that = (AbstractCDOIDByteArray)obj;
-      return Arrays.equals(value, that.value);
-    }
-
-    return false;
-  }
-
-  @Override
-  public int hashCode()
-  {
-    return getClass().hashCode() ^ Arrays.hashCode(value);
-  }
-}
diff --git a/plugins/org.eclipse.emf.cdo.common/src/org/eclipse/emf/cdo/spi/common/id/AbstractCDOIDInteger.java b/plugins/org.eclipse.emf.cdo.common/src/org/eclipse/emf/cdo/spi/common/id/AbstractCDOIDInteger.java
deleted file mode 100644
index 3af3337111..0000000000
--- a/plugins/org.eclipse.emf.cdo.common/src/org/eclipse/emf/cdo/spi/common/id/AbstractCDOIDInteger.java
+++ /dev/null
@@ -1,111 +0,0 @@
-/*
- * Copyright (c) 2004 - 2012 Eike Stepper (Berlin, Germany) and others.
- * All rights reserved. This program and the accompanying materials
- * are made available under the terms of the Eclipse Public License v1.0
- * which accompanies this distribution, and is available at
- * http://www.eclipse.org/legal/epl-v10.html
- *
- * Contributors:
- *    Eike Stepper - initial API and implementation
- *    Simon McDuff - bug 226778
- */
-package org.eclipse.emf.cdo.spi.common.id;
-
-import org.eclipse.net4j.util.io.ExtendedDataInput;
-import org.eclipse.net4j.util.io.ExtendedDataOutput;
-
-import java.io.IOException;
-
-/**
- * If the meaning of this type isn't clear, there really should be more of a description here...
- *
- * @author Eike Stepper
- * @since 2.0
- * @noextend This interface is not intended to be extended by clients.
- */
-public abstract class AbstractCDOIDInteger extends AbstractCDOID
-{
-  private static final long serialVersionUID = 1L;
-
-  private int value;
-
-  public AbstractCDOIDInteger()
-  {
-  }
-
-  public AbstractCDOIDInteger(int value)
-  {
-    if (value == 0)
-    {
-      throw new IllegalArgumentException("value == 0"); //$NON-NLS-1$
-    }
-
-    this.value = value;
-  }
-
-  public int getIntValue()
-  {
-    return value;
-  }
-
-  public String toURIFragment()
-  {
-    return String.valueOf(value);
-  }
-
-  @Override
-  public void read(String fragmentPart)
-  {
-    value = Integer.valueOf(fragmentPart);
-  }
-
-  @Override
-  public void read(ExtendedDataInput in) throws IOException
-  {
-    value = in.readInt();
-  }
-
-  @Override
-  public void write(ExtendedDataOutput out) throws IOException
-  {
-    out.writeInt(value);
-  }
-
-  public int compareTo(AbstractCDOIDInteger that)
-  {
-    if (value < that.value)
-    {
-      return -1;
-    }
-
-    if (value > that.value)
-    {
-      return 1;
-    }
-
-    return 0;
-  }
-
-  @Override
-  public boolean equals(Object obj)
-  {
-    if (obj == this)
-    {
-      return true;
-    }
-
-    if (obj != null && obj.getClass() == getClass())
-    {
-      AbstractCDOIDInteger that = (AbstractCDOIDInteger)obj;
-      return value == that.value;
-    }
-
-    return false;
-  }
-
-  @Override
-  public int hashCode()
-  {
-    return getClass().hashCode() ^ value;
-  }
-}
diff --git a/plugins/org.eclipse.emf.cdo.common/src/org/eclipse/emf/cdo/spi/common/id/AbstractCDOIDLong.java b/plugins/org.eclipse.emf.cdo.common/src/org/eclipse/emf/cdo/spi/common/id/AbstractCDOIDLong.java
deleted file mode 100644
index 1cb2895608..0000000000
--- a/plugins/org.eclipse.emf.cdo.common/src/org/eclipse/emf/cdo/spi/common/id/AbstractCDOIDLong.java
+++ /dev/null
@@ -1,105 +0,0 @@
-/*
- * Copyright (c) 2004 - 2012 Eike Stepper (Berlin, Germany) and others.
- * All rights reserved. This program and the accompanying materials
- * are made available under the terms of the Eclipse Public License v1.0
- * which accompanies this distribution, and is available at
- * http://www.eclipse.org/legal/epl-v10.html
- *
- * Contributors:
- *    Eike Stepper - initial API and implementation
- *    Simon McDuff - bug 226778
- */
-package org.eclipse.emf.cdo.spi.common.id;
-
-import org.eclipse.net4j.util.ObjectUtil;
-import org.eclipse.net4j.util.io.ExtendedDataInput;
-import org.eclipse.net4j.util.io.ExtendedDataOutput;
-
-import java.io.IOException;
-
-/**
- * If the meaning of this type isn't clear, there really should be more of a description here...
- *
- * @author Eike Stepper
- * @since 2.0
- * @noextend This interface is not intended to be extended by clients.
- */
-public abstract class AbstractCDOIDLong extends AbstractCDOID
-{
-  public static final long NULL_VALUE = 0L;
-
-  private static final long serialVersionUID = 1L;
-
-  private long value;
-
-  public AbstractCDOIDLong()
-  {
-  }
-
-  public AbstractCDOIDLong(long value)
-  {
-    if (value == NULL_VALUE)
-    {
-      throw new IllegalArgumentException("value == NULL_VALUE"); //$NON-NLS-1$
-    }
-
-    this.value = value;
-  }
-
-  public long getLongValue()
-  {
-    return value;
-  }
-
-  public String toURIFragment()
-  {
-    return String.valueOf(value);
-  }
-
-  @Override
-  public void read(String fragmentPart)
-  {
-    value = Long.valueOf(fragmentPart);
-  }
-
-  @Override
-  public void read(ExtendedDataInput in) throws IOException
-  {
-    value = in.readLong();
-  }
-
-  @Override
-  public void write(ExtendedDataOutput out) throws IOException
-  {
-    out.writeLong(value);
-  }
-
-  @Override
-  public boolean equals(Object obj)
-  {
-    if (obj == this)
-    {
-      return true;
-    }
-
-    if (obj != null && obj.getClass() == getClass())
-    {
-      AbstractCDOIDLong that = (AbstractCDOIDLong)obj;
-      return value == that.value;
-    }
-
-    return false;
-  }
-
-  @Override
-  public int hashCode()
-  {
-    return getClass().hashCode() ^ ObjectUtil.hashCode(value);
-  }
-
-  @Override
-  public String toString()
-  {
-    return String.valueOf(value);
-  }
-}
diff --git a/plugins/org.eclipse.emf.cdo.common/src/org/eclipse/emf/cdo/spi/common/id/AbstractCDOIDString.java b/plugins/org.eclipse.emf.cdo.common/src/org/eclipse/emf/cdo/spi/common/id/AbstractCDOIDString.java
deleted file mode 100644
index 546cf063d4..0000000000
--- a/plugins/org.eclipse.emf.cdo.common/src/org/eclipse/emf/cdo/spi/common/id/AbstractCDOIDString.java
+++ /dev/null
@@ -1,103 +0,0 @@
-/*
- * Copyright (c) 2004 - 2012 Eike Stepper (Berlin, Germany) and others.
- * All rights reserved. This program and the accompanying materials
- * are made available under the terms of the Eclipse Public License v1.0
- * which accompanies this distribution, and is available at
- * http://www.eclipse.org/legal/epl-v10.html
- *
- * Contributors:
- *    Martin Taal - initial API and implementation
- *    Eike Stepper - maintenance
- */
-package org.eclipse.emf.cdo.spi.common.id;
-
-import org.eclipse.net4j.util.ObjectUtil;
-import org.eclipse.net4j.util.io.ExtendedDataInput;
-import org.eclipse.net4j.util.io.ExtendedDataOutput;
-
-import java.io.IOException;
-
-/**
- * If the meaning of this type isn't clear, there really should be more of a description here...
- *
- * @author Martin Taal
- * @since 3.0
- * @noextend This interface is not intended to be extended by clients.
- */
-public abstract class AbstractCDOIDString extends AbstractCDOID
-{
-  /**
-   * @since 4.0
-   */
-  public static final String NULL_VALUE = null;
-
-  private static final long serialVersionUID = 1L;
-
-  private String value;
-
-  public AbstractCDOIDString()
-  {
-  }
-
-  public AbstractCDOIDString(String value)
-  {
-    this.value = value;
-  }
-
-  public String getStringValue()
-  {
-    return value;
-  }
-
-  public String toURIFragment()
-  {
-    return value;
-  }
-
-  @Override
-  public void read(String fragmentPart)
-  {
-    value = fragmentPart;
-  }
-
-  @Override
-  public void read(ExtendedDataInput in) throws IOException
-  {
-    value = in.readString();
-  }
-
-  @Override
-  public void write(ExtendedDataOutput out) throws IOException
-  {
-    out.writeString(value);
-  }
-
-  @Override
-  public boolean equals(Object obj)
-  {
-    if (obj == this)
-    {
-      return true;
-    }
-
-    if (obj != null && obj.getClass() == getClass())
-    {
-      AbstractCDOIDString that = (AbstractCDOIDString)obj;
-      return value.equals(that.value);
-    }
-
-    return false;
-  }
-
-  @Override
-  public int hashCode()
-  {
-    return getClass().hashCode() ^ ObjectUtil.hashCode(value);
-  }
-
-  @Override
-  public String toString()
-  {
-    return value;
-  }
-}
diff --git a/plugins/org.eclipse.emf.cdo.common/src/org/eclipse/emf/cdo/spi/common/protocol/CDODataInputImpl.java b/plugins/org.eclipse.emf.cdo.common/src/org/eclipse/emf/cdo/spi/common/protocol/CDODataInputImpl.java
index 12eef1d472..d4071cbafb 100644
--- a/plugins/org.eclipse.emf.cdo.common/src/org/eclipse/emf/cdo/spi/common/protocol/CDODataInputImpl.java
+++ b/plugins/org.eclipse.emf.cdo.common/src/org/eclipse/emf/cdo/spi/common/protocol/CDODataInputImpl.java
@@ -632,4 +632,51 @@ public abstract class CDODataInputImpl extends ExtendedDataInput.Delegating impl
   protected abstract CDOListFactory getListFactory();
 
   protected abstract CDOLobStore getLobStore();
+
+  /**
+   * @author Eike Stepper
+   */
+  public static final class Default extends CDODataInputImpl
+  {
+    public Default(ExtendedDataInput delegate)
+    {
+      super(delegate);
+    }
+
+    @Override
+    protected CDORevisionFactory getRevisionFactory()
+    {
+      throw new UnsupportedOperationException();
+    }
+
+    @Override
+    protected CDOPackageRegistry getPackageRegistry()
+    {
+      throw new UnsupportedOperationException();
+    }
+
+    @Override
+    protected CDOLobStore getLobStore()
+    {
+      throw new UnsupportedOperationException();
+    }
+
+    @Override
+    protected CDOListFactory getListFactory()
+    {
+      throw new UnsupportedOperationException();
+    }
+
+    @Override
+    protected CDOCommitInfoManager getCommitInfoManager()
+    {
+      throw new UnsupportedOperationException();
+    }
+
+    @Override
+    protected CDOBranchManager getBranchManager()
+    {
+      throw new UnsupportedOperationException();
+    }
+  }
 }
diff --git a/plugins/org.eclipse.emf.cdo.common/src/org/eclipse/emf/cdo/spi/common/protocol/CDODataOutputImpl.java b/plugins/org.eclipse.emf.cdo.common/src/org/eclipse/emf/cdo/spi/common/protocol/CDODataOutputImpl.java
index 34ab1892f5..da68b883bf 100644
--- a/plugins/org.eclipse.emf.cdo.common/src/org/eclipse/emf/cdo/spi/common/protocol/CDODataOutputImpl.java
+++ b/plugins/org.eclipse.emf.cdo.common/src/org/eclipse/emf/cdo/spi/common/protocol/CDODataOutputImpl.java
@@ -77,7 +77,7 @@ import java.util.Set;
  * @author Eike Stepper
  * @since 4.2
  */
-public abstract class CDODataOutputImpl extends ExtendedDataOutput.Delegating implements CDODataOutput
+public class CDODataOutputImpl extends ExtendedDataOutput.Delegating implements CDODataOutput
 {
   private static final ContextTracer TRACER = new ContextTracer(OM.DEBUG_PROTOCOL, CDODataOutputImpl.class);