diff --git a/src/helma/objectmodel/DbKey.java b/src/helma/objectmodel/DbKey.java
new file mode 100644
index 00000000..28a0a7ab
--- /dev/null
+++ b/src/helma/objectmodel/DbKey.java
@@ -0,0 +1,119 @@
+// DbKey.java
+// Copyright (c) Hannes Wallnöfer 1998-2000
+ 
+package helma.objectmodel;
+
+import java.io.Serializable;
+
+/**
+ * This is the internal representation of a database key. It is constructed 
+ * out of the database URL, the table name, the user name and the database 
+ * key of the node and unique within each Helma application. Currently only
+ * single keys are supported.
+ */
+public final class DbKey implements Key, Serializable {
+
+    private final String storageName;
+    private final String id;
+    private final int hash;
+
+
+    /**
+     * make a key for a persistent Object, describing its datasource and id.
+     */
+    public DbKey (DbMapping dbmap, String id) {
+	this.id = id;
+	this.storageName = dbmap == null ? null : dbmap.getStorageTypeName ();
+	hash = id.hashCode ();
+    }
+
+
+    public boolean equals (Object what) {
+	if (what == this)
+	    return true;
+	try {
+	    DbKey k = (DbKey) what;
+	    return (storageName == k.storageName || storageName.equals (k.storageName)) &&
+	    	(id == k.id || id.equals (k.id));
+	} catch (Exception x) {
+	    return false;
+	}
+    }
+
+    public int hashCode () {
+	return hash;
+    }
+
+    public Key getParentKey () {
+	return null;
+    }
+
+    public String getStorageName () {
+	return storageName;
+    }
+
+    public String getID () {
+	return id;
+    }
+
+
+    public String toString () {
+	return storageName+"["+id+"]";
+    }
+
+
+}
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diff --git a/src/helma/objectmodel/Key.java b/src/helma/objectmodel/Key.java
index 44895c79..e48c8c18 100644
--- a/src/helma/objectmodel/Key.java
+++ b/src/helma/objectmodel/Key.java
@@ -4,86 +4,18 @@
 package helma.objectmodel;
 
 
-import helma.util.CacheMap;
-import java.io.Serializable;
-
 /**
- * This is the internal representation of a database key. It is constructed 
- * out of the database URL, the table name, the user name and the database 
- * key of the node and unique within each Helma application. Currently only
- * single keys are supported.
+ * This is the interface for the internal representation of an object key.
+ *
  */
-public class Key implements Serializable {
-
-    private String type;
-    private String id;
-    private int hash;
-    private boolean virtual;
+public interface Key {
 
 
-    public Key (DbMapping dbmap, String id) {
-	this.type = dbmap == null ? null : dbmap.getStorageTypeName ();
-	this.id = id;
-	hash = id.hashCode ();
-	virtual = false;
-    }
+    public Key getParentKey ();
 
-    public Key (String type, String id) {
-	this.type = type;
-	this.id = id;
-	hash = id.hashCode ();
-	virtual = false;
-    }
-
-    public boolean equals (Object what) {
-	try {
-	    Key k = (Key) what;
-	    return (type == k.type || type.equals (k.type)) && (id == k.id || id.equals (k.id));
-	} catch (Exception x) {
-	    return false;
-	}
-    }
-
-    public int hashCode () {
-	return hash;
-    }
-
-
-    /**
-     *  Get the Key for a virtual node contained by this node, that is, a node that does
-     *   not represent a record in the database. The main objective here is to generate
-     *   a key that can't be mistaken for a relational db key.
-     */
-    public Key getVirtualKey (String sid) {
-	Key k = new Key ((String) null, makeVirtualID (type, id, sid));
-	k.virtual = true;
-	return k;
-    }
-
-    public String getVirtualID (String sid) {
-	return makeVirtualID (type, id, sid);
-    }
-
-    public static String makeVirtualID (DbMapping pmap, String pid, String sid) {
-	return makeVirtualID (pmap == null ? (String) null : pmap.typename, pid, sid);
-    }
-
-    public static String makeVirtualID (String ptype, String pid, String sid) {
-	return ptype+"/"+pid + "~" + sid;
-    }
-
-    public String getType () {
-	return type;
-    }
-
-    public String getID () {
-	return id;
-    }
-
-    public String toString () {
-	return type+"["+id+"]";
-    }
+    public String getID ();
 
+    public String getStorageName ();
 
 }
 
diff --git a/src/helma/objectmodel/SyntheticKey.java b/src/helma/objectmodel/SyntheticKey.java
new file mode 100644
index 00000000..8de44aae
--- /dev/null
+++ b/src/helma/objectmodel/SyntheticKey.java
@@ -0,0 +1,118 @@
+// SyntheticKey.java
+// Copyright (c) Hannes Wallnöfer 1998-2000
+ 
+package helma.objectmodel;
+
+import java.io.Serializable;
+
+/**
+ * This is the internal key for an object that is not stored in a db, but generated
+ * on the fly. Currently there are two kinds of such objects: virtual nodes, which are used
+ * as utility containers for objects in the database, and groupby nodes, which are used
+ * to group a certain kind of relational objects according to some property.
+ */
+public final class SyntheticKey implements Key, Serializable {
+
+    private final Key parentKey;
+    private final String name;
+    private final int hash;
+
+
+    /**
+     * make a key for a persistent Object, describing its datasource and id.
+     */
+    public SyntheticKey (Key key, String name) {
+	this.parentKey = key;
+	this.name = name;
+	hash = name.hashCode () + key.hashCode ();
+    }
+
+
+    public boolean equals (Object what) {
+	try {
+	    SyntheticKey k = (SyntheticKey) what;
+	    return parentKey.equals (k.parentKey) &&
+	    	(name == k.name || name.equals (k.name));
+	} catch (Exception x) {
+	    System.err.println ("SYNTHETIC NOT EQUAL: "+what+" - "+this);
+	    return false;
+	}
+    }
+
+    public int hashCode () {
+	return hash;
+    }
+
+
+    public Key getParentKey () {
+	return parentKey;
+    }
+
+    public String getID () {
+	return name;
+    }
+
+    public String getStorageName () {
+	return null;
+    }
+
+    public String toString () {
+	return parentKey+"/"+name;
+    }
+
+
+}
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