diff --git a/src/helma/objectmodel/db/DbKey.java b/src/helma/objectmodel/db/DbKey.java
new file mode 100644
index 00000000..d5fc2a77
--- /dev/null
+++ b/src/helma/objectmodel/db/DbKey.java
@@ -0,0 +1,122 @@
+// DbKey.java
+// Copyright (c) Hannes Wallnöfer 1998-2000
+ 
+package helma.objectmodel.db;
+
+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 {
+
+    // the name of the prototype which defines the storage of this object.
+    // this is the name of the object's prototype, or one of its ancestors.
+    // If null, the object is stored in the embedded db.
+    private final String storageName;
+    // the id that defines this key's object within the above storage space
+    private final String id;
+
+    /**
+     * 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 ();
+   }
+
+
+
+    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 storageName == null ? id.hashCode () : storageName.hashCode() + id.hashCode ();
+    }
+
+    public Key getParentKey () {
+	return null;
+    }
+
+    public String getStorageName () {
+	return storageName;
+    }
+
+    public String getID () {
+	return id;
+    }
+
+    public String toString () {
+	return storageName == null ? "["+id+"]" : storageName+"["+id+"]";
+    }
+
+
+}
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diff --git a/src/helma/objectmodel/db/DbMapping.java b/src/helma/objectmodel/db/DbMapping.java
new file mode 100644
index 00000000..40e53b78
--- /dev/null
+++ b/src/helma/objectmodel/db/DbMapping.java
@@ -0,0 +1,755 @@
+// DbMapping.java
+// Copyright (c) Hannes Wallnöfer 1998-2000
+
+package helma.objectmodel.db;
+
+import helma.framework.core.Application;
+import helma.util.Updatable;
+import helma.util.SystemProperties;
+import java.util.Hashtable;
+import java.util.Enumeration;
+import java.util.StringTokenizer;
+import java.sql.*;
+import com.workingdogs.village.*;
+
+/** 
+  * A DbMapping describes how a certain type of  Nodes is to mapped to a 
+  * relational database table. Basically it consists of a set of JavaScript property-to-
+  * Database row bindings which are represented by instances of the Relation class.
+  */
+  
+public class DbMapping implements Updatable {
+
+    // DbMappings belong to an application
+    Application app;
+    // prototype name of this mapping
+    String typename;
+
+    // properties from where the mapping is read
+    SystemProperties props;
+
+    // name of data source to which this mapping writes
+    DbSource source;
+    // name of datasource
+    String sourceName;
+    // name of db table
+    String table;
+
+    // list of properties to try for parent
+    ParentInfo[] parent;
+    // list of properties to try as skinmanager
+    String[] skinmgr;
+
+    // DbMapping subnodes;
+    // DbMapping properties;
+    Relation subnodesRel;
+    Relation propertiesRel;
+
+    // if this defines a subnode mapping with groupby layer, we need a DbMapping for those groupby nodes
+    DbMapping groupbyMapping;
+
+     // Map of property names to Relations objects
+    Hashtable prop2db;
+     // Map of db columns to Relations objects
+    Hashtable db2prop;
+
+    // db field used as primary key
+    String idField;
+    // db field used as object name
+    String nameField;
+    // db field used to identify name of prototype to use for object instantiation
+    String protoField;
+
+    // name of parent prototype, if any
+    String extendsProto;
+    // dbmapping of parent prototype, if any
+    DbMapping parentMapping;
+    boolean inheritsMapping;
+
+    // db field that specifies the prototype of an object
+    String prototypeField;
+
+    // descriptor for key generation method
+    private String idgen;
+    // remember last key generated for this table
+    long lastID;
+
+    // the (village) schema of the database table
+    Schema schema = null;
+    // the (village) keydef of the db table
+    KeyDef keydef = null;
+
+    // timestamp of last modification of the mapping (type.properties)
+    long lastTypeChange;
+    // timestamp of last modification of an object of this type
+    long lastDataChange;
+
+
+    /**
+     * Create an empty DbMapping
+     */
+    public DbMapping () {
+
+	prop2db = new Hashtable ();
+	db2prop = new Hashtable ();
+
+	parent = null;
+	// subnodes = null;
+	// properties = null;
+	idField = "id";
+    }
+
+    /**
+     * Create a DbMapping from a type.properties property file
+     */
+    public DbMapping (Application app, String typename, SystemProperties props) {
+
+	this.app = app;
+	this.typename = typename;
+
+	prop2db = new Hashtable ();
+	db2prop = new Hashtable ();
+
+	parent = null;
+	// subnodes = null;
+	// properties = null;
+	idField = "id";
+
+	this.props = props;
+	update ();
+
+	app.putDbMapping (typename, this);
+    }
+
+    /**
+     * Tell the type manager whether we need update() to be called
+     */
+    public boolean needsUpdate () {
+	return props.lastModified () != lastTypeChange;
+    }
+
+
+    /**
+     * Read the mapping from the Properties. Return true if the properties were changed.
+     * The read is split in two, this method and the rewire method. The reason is that in order
+     * for rewire to work, all other db mappings must have been initialized and registered.
+     */
+    public synchronized void update () {
+
+	table = props.getProperty ("_tablename");
+	idgen = props.getProperty ("_idgen");
+	// see if there is a field which specifies the prototype of objects, if different prototypes
+	// can be stored in this table
+	prototypeField = props.getProperty ("_prototypefield");
+	// see if this prototype extends (inherits from) any other prototype
+	extendsProto = props.getProperty ("_extends");
+	
+	sourceName = props.getProperty ("_datasource");
+	if (sourceName != null) {
+	    source = app.getDbSource (sourceName);
+	    if (source == null) {
+	        app.logEvent ("*** Data Source for prototype "+typename+" does not exist: "+sourceName);
+	        app.logEvent ("*** accessing or storing a "+typename+" object will cause an error.");
+	    }
+	}
+
+	// id field must not be null, default is "id"
+	idField = props.getProperty ("_id", "id");
+
+	nameField = props.getProperty ("_name");
+
+	protoField = props.getProperty ("_prototype");
+	
+	String parentMapping = props.getProperty ("_parent");
+	if (parentMapping != null) {
+	    // comma-separated list of properties to be used as parent
+	    StringTokenizer st = new StringTokenizer (parentMapping, ",;");
+	    parent = new ParentInfo[st.countTokens()];
+	    for (int i=0; i<parent.length; i++)
+	        parent[i] = new ParentInfo (st.nextToken().trim());
+	} else
+	    parent = null;
+	
+	String skm = props.getProperty ("_skinmanager");
+	if (skm != null) {
+	    StringTokenizer st = new StringTokenizer (skm, ",;");
+	    skinmgr = new String[st.countTokens()];
+	    for (int i=0; i<skinmgr.length; i++)
+	        skinmgr[i] = st.nextToken().trim();
+	} else
+	    skinmgr = null;
+
+	lastTypeChange = props.lastModified ();
+	// set the cached schema & keydef to null so it's rebuilt the next time around
+	schema = null;
+	keydef = null;
+    }
+
+    /**
+     * This is the second part of the property reading process, called after the first part has been
+     * completed on all other mappings in this application
+     */
+    public synchronized void rewire () {
+
+	if (extendsProto != null) {
+	    parentMapping = app.getDbMapping (extendsProto);
+	}
+	
+	// if (table != null && source != null) {
+	// app.logEvent ("set data source for "+typename+" to "+source);
+	Hashtable p2d = new Hashtable ();
+	Hashtable d2p = new Hashtable ();
+
+	for (Enumeration e=props.keys(); e.hasMoreElements(); ) {
+	    String propName = (String) e.nextElement ();
+
+	    try {
+	        if (!propName.startsWith ("_") && propName.indexOf (".") < 0) {
+	            String dbField = props.getProperty (propName);
+	            // check if a relation for this propery already exists. If so, reuse it
+	            Relation rel = propertyToRelation (propName);
+	            if (rel == null)
+	                rel = new Relation (dbField, propName, this, props);
+	            else
+	                rel.update (dbField, props);
+	            p2d.put (propName, rel);
+	            if (rel.columnName != null &&
+	            		(rel.reftype == Relation.PRIMITIVE ||
+	            		rel.reftype == Relation.REFERENCE))
+	                d2p.put (rel.columnName, rel);
+	            // app.logEvent ("Mapping "+propName+" -> "+dbField);
+	        }
+	    } catch (Exception x) {
+	        app.logEvent ("Error in type.properties: "+x.getMessage ());
+	    }
+	}
+
+	prop2db = p2d;
+	db2prop = d2p;
+
+	String subnodeMapping = props.getProperty ("_subnodes");
+	if (subnodeMapping != null) {
+	    try {
+	        // check if subnode relation already exists. If so, reuse it
+	        if (subnodesRel == null)
+	            subnodesRel = new Relation (subnodeMapping, "_subnodes", this, props);
+	        else
+	            subnodesRel.update (subnodeMapping, props);
+	        // if (subnodesRel.isReference ())
+	            // subnodes = subnodesRel.other;
+	        // else
+	        //     subnodes = (DbMapping) app.getDbMapping (subnodeMapping);
+	    } catch (Exception x) {
+	        app.logEvent ("Error reading _subnodes relation for "+typename+": "+x.getMessage ());
+	        // subnodesRel = null;
+	    }
+	} else
+	    subnodesRel = null;
+
+	String propertiesMapping = props.getProperty ("_properties");
+	if (propertiesMapping != null) {
+	    try {
+	        // check if property relation already exists. If so, reuse it
+	        if (propertiesRel == null)
+	            propertiesRel = new Relation (propertiesMapping, "_properties", this, props);
+	        else
+	            propertiesRel.update (propertiesMapping, props);
+	        // if (propertiesRel.isReference ())
+	        //     properties = propertiesRel.other;
+	        // else
+	        //     properties = (DbMapping) app.getDbMapping (propertiesMapping);
+	        // take over groupby flag from subnodes, if properties are subnodes
+	        if (propertiesRel.subnodesAreProperties && subnodesRel != null)
+	            propertiesRel.groupby = subnodesRel.groupby;
+	    } catch (Exception x) {
+	        app.logEvent ("Error reading _properties relation for "+typename+": "+x.getMessage ());
+	        // propertiesRel = null;
+	    }
+	} else
+	    propertiesRel = null;
+
+	if (groupbyMapping != null) {
+	    groupbyMapping.subnodesRel = subnodesRel == null ? null : subnodesRel.getGroupbySubnodeRelation ();
+	    groupbyMapping.propertiesRel = propertiesRel == null ? null : propertiesRel.getGroupbyPropertyRelation ();
+	    groupbyMapping.lastTypeChange = this.lastTypeChange;
+	}
+    }
+
+
+
+    public Connection getConnection () throws ClassNotFoundException, SQLException {
+	// if source was previously not available, check again
+	if (source == null && sourceName != null)
+	    source = app.getDbSource (sourceName);
+	if (sourceName == null && parentMapping != null)
+	    return parentMapping.getConnection ();
+	if (source == null) {
+	    if (sourceName == null)
+	        throw new SQLException ("Tried to get Connection from non-relational embedded data source.");
+	    else
+	        throw new SQLException ("Datasource is not defined: "+sourceName+".");
+	}
+	return source.getConnection ();
+    }
+
+    public DbSource getDbSource () {
+	if (source == null && parentMapping != null)
+	    return parentMapping.getDbSource ();
+	return source;
+    }
+
+    public String getSourceID () {
+	if (source == null && parentMapping != null)
+	    return parentMapping.getSourceID ();
+	return source == null ? "" : source.url;
+    }
+
+    public String getTableName () {
+	if (source == null && parentMapping != null)
+	    return parentMapping.getTableName ();
+	return table;
+    }
+
+    public Application getApplication () {
+	return app;
+    }
+
+    public String getAppName () {
+	return app.getName();
+    }
+
+    public String getTypeName () {
+	return typename;
+    }
+
+    public String getExtends () {
+	return extendsProto;
+    }
+
+    /**
+     * Get the primary key column name for objects using this mapping.
+     */
+    public String getIDField () {
+    	if (idField == null && parentMapping != null)
+	    return parentMapping.getIDField ();
+	return idField;
+    }
+
+    /**
+     * Get the column used for (internal) names of objects of this type.
+     */
+    public String getNameField () {
+    	if (nameField == null && parentMapping != null)
+	    return parentMapping.getNameField ();
+	return nameField;
+    }
+
+    /**
+     * Get the column used for names of prototype.
+     */
+    public String getPrototypeField () {
+    	if (protoField == null && parentMapping != null)
+	    return parentMapping.getPrototypeField ();
+	return protoField;
+    }
+
+
+    /**
+     * Translate a database column name to an object property name according to this mapping.
+     */
+    public String columnNameToProperty (String columnName) {
+	if (columnName == null)
+	    return null;
+	if (table == null && parentMapping != null)
+	    return parentMapping.columnNameToProperty (columnName);
+	Relation rel = (Relation) db2prop.get (columnName);
+	if (rel != null  && (rel.reftype == Relation.PRIMITIVE || rel.reftype == Relation.REFERENCE))
+	    return rel.propName;
+	return null;
+    }
+
+    /**
+     * Translate an object property name to a database column name according to this mapping.
+     */
+    public String propertyToColumnName (String propName) {
+	if (propName == null)
+	    return null;
+	if (table == null && parentMapping != null)
+	    return parentMapping.propertyToColumnName (propName);
+	Relation rel = (Relation) prop2db.get (propName);
+	if (rel != null  && (rel.reftype == Relation.PRIMITIVE || rel.reftype == Relation.REFERENCE))
+	    return rel.columnName;
+	return null;
+    }
+
+    /**
+     * Translate a database column name to an object property name according to this mapping.
+     */
+    public Relation columnNameToRelation (String columnName) {
+	if (columnName == null)
+	    return null;
+	if (table == null && parentMapping != null)
+	    return parentMapping.columnNameToRelation (columnName);
+	return (Relation) db2prop.get (columnName);
+    }
+
+    /**
+     * Translate an object property name to a database column name according to this mapping.
+     */
+    public Relation propertyToRelation (String propName) {
+	if (propName == null)
+	    return null;
+	if (table == null && parentMapping != null)
+	    return parentMapping.propertyToRelation (propName);
+	return (Relation) prop2db.get (propName);
+    }
+
+
+    public synchronized ParentInfo[] getParentInfo () {
+    	if (parent == null && parentMapping != null)
+    	    return parentMapping.getParentInfo ();
+	return parent;
+    }
+
+    public String[] getSkinManagers () {
+	return skinmgr;
+    }
+
+
+    public DbMapping getSubnodeMapping () {
+	if (subnodesRel != null)
+	    return subnodesRel.otherType;
+    	if (parentMapping != null)
+    	    return parentMapping.getSubnodeMapping ();
+	return null;
+    }
+
+
+    public DbMapping getExactPropertyMapping (String propname) {
+	if (propname == null)
+	    return null;
+	Relation rel = (Relation) prop2db.get (propname.toLowerCase());
+	if (rel == null && parentMapping != null)
+	    return parentMapping.getExactPropertyMapping (propname);
+	return rel != null ? rel.otherType : null;
+    }
+
+    public DbMapping getPropertyMapping (String propname) {
+	if (propname == null) {
+	    if (propertiesRel != null)
+	        return propertiesRel.otherType;
+	    if (parentMapping != null)
+	        return parentMapping.getPropertyMapping (null);
+	}
+	
+	Relation rel = (Relation) prop2db.get (propname.toLowerCase());
+	if (rel != null) {
+	    // if this is a virtual node, it doesn't have a dbmapping
+	    if (rel.virtual && rel.prototype == null)
+	        return null;
+	    else
+	        return rel.otherType;
+	}
+	
+	if (propertiesRel != null)
+	    return propertiesRel.otherType;
+	if (parentMapping != null)
+	    return parentMapping.getPropertyMapping (propname);
+	return null;
+    }
+
+    public DbMapping getGroupbyMapping () {
+	if (subnodesRel == null || subnodesRel.groupby == null)
+	    return null;
+	if (groupbyMapping == null) {
+	    groupbyMapping = new DbMapping ();
+	    groupbyMapping.subnodesRel = subnodesRel.getGroupbySubnodeRelation ();
+	    if (propertiesRel != null)
+	        groupbyMapping.propertiesRel = propertiesRel.getGroupbyPropertyRelation ();
+	    else
+	        groupbyMapping.propertiesRel = subnodesRel.getGroupbyPropertyRelation ();
+	    groupbyMapping.typename = subnodesRel.groupbyprototype;
+	}
+	return groupbyMapping;
+    }
+
+    /* public void setPropertyMapping (DbMapping pm) {
+	properties = pm;
+    } */
+
+    public void setSubnodeRelation (Relation rel) {
+	subnodesRel = rel;
+    }
+
+    public void setPropertyRelation (Relation rel) {
+	propertiesRel = rel;
+    }
+
+    public Relation getSubnodeRelation () {
+	if (subnodesRel == null && parentMapping != null)
+	    return parentMapping.getSubnodeRelation ();
+	return subnodesRel;
+    }
+
+    public Relation getPropertyRelation () {
+	if (propertiesRel == null && parentMapping != null)
+	    return parentMapping.getPropertyRelation ();
+	return propertiesRel;
+    }
+
+    public Relation getPropertyRelation (String propname) {
+	if (propname == null)
+	    return getPropertyRelation ();
+	Relation rel = (Relation) prop2db.get (propname.toLowerCase());
+	if (rel == null && propertiesRel == null && parentMapping != null)
+	    return parentMapping.getPropertyRelation (propname);
+	return rel != null ? rel : propertiesRel;
+    }
+
+    public String getSubnodeGroupby () {
+	if (subnodesRel == null && parentMapping != null)
+	    return parentMapping.getSubnodeGroupby ();
+	return subnodesRel == null ? null : subnodesRel.groupby;
+    }
+
+    public String getIDgen () {
+	if (idgen == null && parentMapping != null)
+	    return parentMapping.getIDgen ();
+	return idgen;
+    }
+
+
+    public WrappedNodeManager getWrappedNodeManager () {
+	if (app == null)
+	   throw new RuntimeException ("Can't get node manager from internal db mapping");
+	return app.getWrappedNodeManager ();
+    }
+
+    /**
+     *  Tell whether this data mapping maps to a relational database table. This returns true
+     *  if a datasource is specified, even if it is not a valid one. Otherwise, objects with invalid
+     *  mappings would be stored in the embedded db instead of an error being thrown, which is
+     *  not what we want.
+     */
+    public boolean isRelational () {
+	if (sourceName != null)
+	    return true;
+	if (parentMapping != null)
+	    return parentMapping.isRelational ();
+	return false;
+    }
+
+    /**
+     * Return a Village Schema object for this DbMapping.
+     */
+    public synchronized Schema getSchema () throws ClassNotFoundException, SQLException, DataSetException {
+	if (!isRelational ())
+	    throw new SQLException ("Can't get Schema for non-relational data mapping");
+    	if (source == null && parentMapping != null)
+	    return parentMapping.getSchema ();
+	// Use local variable s to avoid synchronization (schema may be nulled elsewhere)
+	Schema s = schema;
+	if (s != null)
+	    return s;
+	schema = new Schema ().schema (getConnection (), table, "*");
+	return schema;	
+    }
+
+    /**
+     * Return a Village Schema object for this DbMapping.
+     */
+    public synchronized KeyDef getKeyDef () {
+	if (!isRelational ())
+	    throw new RuntimeException ("Can't get KeyDef for non-relational data mapping");
+    	if (source == null && parentMapping != null)
+	    return parentMapping.getKeyDef ();
+	// Use local variable s to avoid synchronization (keydef may be nulled elsewhere)
+	KeyDef k = keydef;
+	if (k != null)
+	    return k;
+	keydef = new KeyDef ().addAttrib (idField);
+	return keydef;	
+    }
+
+    public String toString () {
+	if (app == null)
+	    return "[unspecified internal DbMapping]";
+	else
+	    return ("["+app.getName()+"."+typename+"]");
+    }
+
+    public long getLastTypeChange () {
+	return lastTypeChange;
+    }
+
+
+    public long getLastDataChange () {
+	return lastDataChange;
+    }
+
+    public void notifyDataChange () {
+	lastDataChange = System.currentTimeMillis ();
+	if (parentMapping != null && source == null)
+	    parentMapping.notifyDataChange ();
+    }
+
+    public synchronized long getNewID (long dbmax) {
+	if (parentMapping != null && source == null)
+	    return parentMapping.getNewID (dbmax);
+	lastID = Math.max (dbmax+1, lastID+1);
+	return lastID;
+    }
+
+    public Hashtable getProp2DB () {
+	if (table == null && parentMapping != null)
+	    return parentMapping.getProp2DB ();
+	return prop2db;
+    }
+
+    public Hashtable getDB2Prop () {
+	if (table == null && parentMapping != null)
+	    return parentMapping.getDB2Prop ();
+	return db2prop;
+    }
+
+    /**
+     *  Return the name of the prototype which specifies the storage location
+     * (dbsource + tablename) for this type, or null if it is stored in the embedded
+     * db.
+     */
+    public String getStorageTypeName () {
+	if (table == null && parentMapping != null)
+	    return parentMapping.getStorageTypeName ();
+	return sourceName == null ? null : typename;
+    }
+
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diff --git a/src/helma/objectmodel/db/DbSource.java b/src/helma/objectmodel/db/DbSource.java
new file mode 100644
index 00000000..b853e65d
--- /dev/null
+++ b/src/helma/objectmodel/db/DbSource.java
@@ -0,0 +1,121 @@
+// DbSource.java
+// Copyright (c) Hannes Wallnöfer 1999-2000
+
+package helma.objectmodel.db;
+
+import java.sql.*;
+import java.util.Hashtable;
+import helma.util.SystemProperties;
+ 
+/**
+ *  This class describes a releational data source (URL, driver, user and password).
+ */
+
+public class DbSource {
+
+    private String name;
+    private SystemProperties props;
+    private static SystemProperties defaultProps = null;
+    protected String url;
+    private String driver;
+    protected String user;
+    private String password;
+
+    private long lastRead = 0l;
+
+    public DbSource (String name, SystemProperties props) throws ClassNotFoundException {
+	this.name = name;
+	this.props = props;
+	init ();
+	Server.getLogger().log ("created db source ["+name+", "+url+", "+driver+", "+user+"]");
+    }
+
+    public Connection getConnection () throws ClassNotFoundException, SQLException {
+	Transactor tx = (Transactor) Thread.currentThread ();
+	Connection con = tx.getConnection (this);
+	boolean fileUpdated = props.lastModified () > lastRead;
+	if (!fileUpdated && defaultProps != null)
+	    fileUpdated = defaultProps.lastModified () > lastRead;
+	if (con == null || con.isClosed () || fileUpdated) {
+	    init ();
+	    Class.forName (driver);
+	    con = DriverManager.getConnection (url, user, password);
+	    // If we wanted to use SQL transactions, we'd set autoCommit to
+	    // false here and make commit/rollback invocations in Transactor methods;
+	    Server.getLogger().log ("Created new Connection to "+url);
+	    tx.registerConnection (this, con);
+	    //////////////////////////////////////////////
+	   /*  DatabaseMetaData meta = con.getMetaData ();
+	    ResultSet tables = meta.getCatalogs ();
+	    while (tables.next())
+	        System.err.println ("********* TABLE: "+ tables.getObject (1));
+	    ResultSet types = meta.getTypeInfo ();
+	    while (types.next())
+	        System.err.println ("******* TYPE: "+types.getObject(1) +" - "+types.getObject(2)+" - "+types.getObject(6));
+	    */
+	}
+	return con;
+    }
+
+    private void init () throws ClassNotFoundException {
+	lastRead = defaultProps == null ? props.lastModified () : Math.max (props.lastModified (), defaultProps.lastModified ());
+	url = props.getProperty (name+".url");
+	driver = props.getProperty (name+".driver");
+	Class.forName (driver);
+	user = props.getProperty (name+".user");
+	password = props.getProperty (name+".password");
+    }
+
+    public String getDriverName () {
+	return driver;
+    }
+
+    public String getName () {
+	return name;
+    }
+
+    public static void setDefaultProps (SystemProperties props) {
+	defaultProps = props;
+    }
+
+}
+
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diff --git a/src/helma/objectmodel/db/Key.java b/src/helma/objectmodel/db/Key.java
new file mode 100644
index 00000000..f48d66ab
--- /dev/null
+++ b/src/helma/objectmodel/db/Key.java
@@ -0,0 +1,74 @@
+// Key.java
+// Copyright (c) Hannes Wallnöfer 1998-2000
+ 
+package helma.objectmodel.db;
+
+
+/**
+ * This is the interface for the internal representation of an object key.
+ *
+ */
+public interface Key {
+
+
+    public Key getParentKey ();
+
+    public String getID ();
+
+    public String getStorageName ();
+
+}
+
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diff --git a/src/helma/objectmodel/db/ParentInfo.java b/src/helma/objectmodel/db/ParentInfo.java
new file mode 100644
index 00000000..4931e013
--- /dev/null
+++ b/src/helma/objectmodel/db/ParentInfo.java
@@ -0,0 +1,41 @@
+// ParentInfo.java
+// Copyright (c) Hannes Wallnöfer 1999-2000
+
+package helma.objectmodel.db;
+
+
+/**
+ *  This class describes a parent relation between releational nodes.
+ */
+
+public class ParentInfo {
+
+    public final String propname;
+    public final String virtualname;
+    public final boolean named;
+    public final boolean isroot;
+
+
+    public ParentInfo (String desc) {
+	int n = desc.indexOf ("[named]");
+	named = n > -1;
+	String d = named ? desc.substring (0, n) : desc;
+
+	int dot = d.indexOf (".");
+	if (dot > -1) {
+	    propname = d.substring (0, dot).trim();
+	    virtualname = d.substring (dot+1).trim();
+	} else {
+	    propname = d.trim();
+	    virtualname = null;
+	}
+	
+	isroot = "root".equals (propname);
+	// System.err.println ("created "+this);
+    }	
+
+    public String toString () {
+	return "ParentInfo["+propname+","+virtualname+","+named+"]";
+    }
+
+}
diff --git a/src/helma/objectmodel/db/Relation.java b/src/helma/objectmodel/db/Relation.java
new file mode 100644
index 00000000..a908fd93
--- /dev/null
+++ b/src/helma/objectmodel/db/Relation.java
@@ -0,0 +1,655 @@
+// Relation.java
+// Copyright (c) Hannes Wallnöfer 1997-2000
+ 
+package helma.objectmodel.db;
+
+import helma.objectmodel.*;
+import helma.framework.core.Application;
+import java.util.Properties;
+import java.util.Vector;
+
+/**
+ * This describes how a property of a persistent Object is stored in a
+ *  relational database table. This can be either a scalar property (string, date, number etc.)
+ *  or a reference to one or more other objects.
+ */
+public class Relation {
+
+    // these constants define different type of property-to-db-mappings
+
+    // there is an error in the description of this relation
+    public final static int INVALID = -1;
+     // a mapping of a non-object, scalar type
+    public final static int PRIMITIVE = 0;
+     // a 1-to-1 relation, i.e. a field in the table is a foreign key to another object
+    public final static int REFERENCE = 1;
+    // a 1-to-many relation, a field in another table points to objects of this type
+    public final static int COLLECTION = 2;
+    // direct mapping is a very powerful feature: objects of some types can be directly accessed
+    // by one of their properties/db fields.
+    // public final static int DIRECT = 3;
+
+    // the DbMapping of the type we come from
+    public DbMapping ownType;
+    // the DbMapping of the prototype we link to, unless this is a "primitive" (non-object) relation
+    public DbMapping otherType;
+
+    //  if this relation defines a virtual node, we need to provide a DbMapping for these virtual nodes
+    DbMapping virtualMapping;
+
+    Relation virtualRelation;
+    Relation groupRelation;
+
+    public String propName;
+    protected String columnName;
+
+    public int reftype;
+
+    public Constraint[] constraints;
+
+    public boolean virtual;
+    public boolean readonly;
+    public boolean aggressiveLoading;
+    public boolean aggressiveCaching;
+    public boolean subnodesAreProperties;
+    public String accessor; // db column used to access objects through this relation
+    public String order;
+    public String groupbyorder;
+    public String groupby;
+    public String dogroupby;
+    public String prototype;
+    public String groupbyprototype;
+    public String filter;
+
+    // Relation subnoderelation = null; // additional relation used to filter subnodes for virtual nodes
+
+    /**
+     * This constructor makes a copy of an existing relation. Not all fields are copied, just those
+     * which are needed in groupby- and virtual nodes defined by this relation.
+     */
+    public Relation (Relation rel) {
+	this.ownType = rel.ownType;
+	this.otherType = rel.otherType;
+	this.propName = rel.propName;
+	this.columnName = rel.columnName;
+	this.reftype = rel.reftype;
+	this.constraints = rel.constraints;
+	this.accessor = rel.accessor;
+	this.subnodesAreProperties = rel.subnodesAreProperties;
+    }
+
+    /**
+     * Reads a relation entry from a line in a properties file.
+     */
+    public Relation (String desc, String propName, DbMapping ownType, Properties props) {
+	this.ownType = ownType;
+	this.propName = propName;
+	otherType = null;
+	
+	update (desc, props);
+    }
+
+    public void update (String desc, Properties props) {
+	
+	boolean mountpoint = false;
+	Vector cnst = null;
+
+	if (desc == null || "".equals (desc.trim ())) {
+	    if (propName != null) {
+	        reftype = PRIMITIVE;
+	        columnName = propName;
+	    } else {
+	        reftype = INVALID;
+	        columnName = propName;
+	    }
+	} else {
+	    desc = desc.trim ();
+	    String descLower = desc.toLowerCase ();
+	    if (descLower.startsWith ("[virtual]")) {
+	        desc = desc.substring (9).trim ();
+	        virtual = true;
+	    } else if (descLower.startsWith ("[collection]")) {
+	        desc = desc.substring (12).trim ();
+	        virtual = true;
+	    } else if (descLower.startsWith ("[mountpoint]")) {
+	        desc = desc.substring (12).trim ();
+	        virtual = true;
+	        mountpoint = true;
+	    } else {
+	        virtual = false;
+	    }
+	    if (descLower.startsWith ("[readonly]")) {
+	        desc = desc.substring (10).trim ();
+	        readonly = true;
+	    } else {
+	        readonly = false;
+	    }
+	}
+	
+	// parse the basic properties of this mapping
+	parseMapping (desc, mountpoint);
+	
+	// the following options only apply to object relations
+	if (reftype != PRIMITIVE && reftype != INVALID) {
+	
+	    cnst = new Vector ();
+	
+	    Constraint c = parseConstraint (desc);
+	
+	    if (c != null)
+	        cnst.add (c);
+	
+	    parseOptions (cnst, props);
+	
+	    constraints = new Constraint[cnst.size()];
+	    cnst.copyInto (constraints);
+
+	    // System.err.println ("PARSED RELATION "+this);
+	    // if (accessor != null)
+	    //     System.err.println ("SET ACCESSOR: "+accessor);
+	}
+    }
+
+    /**
+     * Parse a line describing a mapping of a property field. If the mapping is a
+     * object reference of a collection of objects, put any constraints in the Vector.
+     */
+    protected void parseMapping (String desc, boolean mountpoint) {
+	
+	Application app = ownType.getApplication ();
+	
+	if (desc.indexOf ("<") > -1) {
+	    reftype = COLLECTION;
+	    int lt = desc.indexOf ("<");
+	    int dot = desc.indexOf (".");
+	    String other = dot < 0 ? desc.substring (lt+1).trim () : desc.substring (lt+1, dot).trim ();
+	    otherType = app.getDbMapping (other);
+	    if (otherType == null)
+	        throw new RuntimeException ("DbMapping for "+other+" not found from "+ownType.typename);
+	    columnName = null;
+	    if (mountpoint)
+	        prototype = other;
+	} else if (desc.indexOf (">") > -1) {
+	    reftype = REFERENCE;
+	    int bt = desc.indexOf (">");
+	    int dot = desc.indexOf (".");
+	    String other = dot > -1 ? desc.substring (bt+1, dot).trim () : desc.substring (bt+1).trim ();
+	    otherType = app.getDbMapping (other);
+	    if (otherType == null)
+	        throw new RuntimeException ("DbMapping for "+other+" not found from "+ownType.typename);
+	    columnName = desc.substring (0, bt).trim ();
+	    if (mountpoint)
+	        prototype = other;
+	} else if (desc.indexOf (".") > -1) {
+	    reftype = COLLECTION;
+	    int dot = desc.indexOf (".");
+	    String other = desc.substring (0, dot).trim ();
+	    otherType = app.getDbMapping (other);
+	    if (otherType == null)
+	        throw new RuntimeException ("DbMapping for "+other+" not found from "+ownType.typename);
+	    columnName = null;
+	    // set accessor
+	    accessor = desc.substring (dot+1).trim ();
+	    if (mountpoint)
+	        prototype = other;
+	} else {
+	    if (virtual) {
+	        reftype = COLLECTION;
+	        otherType = app.getDbMapping (desc);
+	        if (otherType == null)
+	            throw new RuntimeException ("DbMapping for "+desc+" not found from "+ownType.typename);
+	        if (mountpoint)
+	            prototype = desc;
+	    } else {
+	        reftype = PRIMITIVE;
+	        columnName = desc.trim ();
+	    }
+	}
+    }
+
+
+    /**
+     * Parse a line describing a mapping of a property field. If the mapping is a
+     * object reference of a collection of objects, put any constraints in the Vector.
+     */
+    protected Constraint parseConstraint (String desc) {
+	if (desc.indexOf ("<") > -1) {
+	    int lt = desc.indexOf ("<");
+	    int dot = desc.indexOf (".");
+	    String remoteField = dot < 0 ? null : desc.substring (dot+1).trim ();
+	    String localField = lt <= 0 ? null : desc.substring (0, lt).trim ();
+	    return new Constraint (localField, otherType.getTableName (), remoteField, false);
+	} else if (desc.indexOf (">") > -1) {
+	    int bt = desc.indexOf (">");
+	    int dot = desc.indexOf (".");
+	    String localField = desc.substring (0, bt).trim ();
+	    String remoteField = dot < 0 ? null : desc.substring (dot+1).trim ();
+	    return new Constraint (localField, otherType.getTableName (), remoteField, false);
+	}
+	return null;
+    }
+
+    protected void parseOptions (Vector cnst, Properties props) {
+	String loading = props.getProperty (propName+".loadmode");
+	aggressiveLoading = loading != null && "aggressive".equalsIgnoreCase (loading.trim());
+	String caching = props.getProperty (propName+".cachemode");
+	aggressiveCaching = caching != null && "aggressive".equalsIgnoreCase (caching.trim());
+	// get order property
+	order = props.getProperty (propName+".order");
+	if (order != null && order.trim().length() == 0)
+	    order = null;
+	// get additional filter property
+	filter = props.getProperty (propName+".filter");
+	if (filter != null && filter.trim().length() == 0)
+	    filter = null;
+	// get group by property
+	groupby = props.getProperty (propName+".groupby");
+	if (groupby != null && groupby.trim().length() == 0)
+	    groupby = null;
+	if (groupby != null) {
+	    groupbyorder = props.getProperty (propName+".groupby.order");
+	    if (groupbyorder != null && groupbyorder.trim().length() == 0)
+	        groupbyorder = null;
+	    groupbyprototype = props.getProperty (propName+".groupby.prototype");
+	    if (groupbyprototype != null && groupbyprototype.trim().length() == 0)
+	        groupbyprototype = null;
+	    // aggressive loading and caching is not supported for groupby-nodes
+	    aggressiveLoading = aggressiveCaching = false;
+	}
+	// check if subnode condition should be applied for property relations
+	if ("_properties".equalsIgnoreCase (propName) || virtual) {
+	    String subnodes2props = props.getProperty (propName+".aresubnodes");
+	    subnodesAreProperties = "true".equalsIgnoreCase (subnodes2props);
+	    if (virtual) {
+	        String subnodefilter = props.getProperty (propName+".subnoderelation");
+	        if (subnodefilter != null) {
+	            Constraint c = parseConstraint (subnodefilter);
+	            if (c != null) {
+	                cnst.add (c);
+	            }
+	        }
+	    }
+	    // update virtual mapping, if it already exists
+	    if (virtualMapping != null) {
+	        virtualMapping.subnodesRel = getVirtualSubnodeRelation ();
+	        virtualMapping.propertiesRel = getVirtualPropertyRelation ();
+	        virtualMapping.lastTypeChange = ownType.lastTypeChange;
+	    }
+	}
+    }
+
+
+    /**
+     * Add a constraint to the current list of constraints
+     */
+    protected void addConstraint (Constraint c) {
+ 	if (constraints == null) {
+ 	    constraints = new Constraint[1];
+ 	    constraints[0] = c;
+ 	} else {
+ 	    Constraint[] nc = new Constraint[constraints.length+1];
+ 	    System.arraycopy (constraints, 0, nc, 0, constraints.length);
+ 	    nc[nc.length-1] = c;
+ 	    constraints = nc;
+ 	}
+    }
+
+
+    public boolean usesPrimaryKey () {
+	if (otherType != null) {
+	    if (reftype == REFERENCE)
+	        return constraints.length == 1 && constraints[0].foreignKeyIsPrimary ();
+	    if (reftype == COLLECTION)
+	        return accessor == null || accessor.equals (otherType.getIDField ());
+	}
+	return false;
+	/*
+	if (otherType == null)
+	    return false;
+	if (remoteField == null)
+	    // if remote field is null, it is assumed that it points to the primary key
+	    return true;
+	return remoteField.equalsIgnoreCase (otherType.getIDField()); */
+    }
+
+    public Relation getSubnodeRelation () {
+	// return subnoderelation;
+	return null;
+    }
+
+
+    /**
+     * Return the local field name for updates.
+     */
+    public String getDbField () {
+	return columnName;
+    }
+
+
+    /**
+     * Get the local column name for this relation to use in where clauses of select statements.
+     * This uses the home node's id as fallback if local field is not specified.
+     */
+    /* public String[] getLocalFields () {
+	if (constraints == null)
+	    return new String[0];
+	String[] retval = new String[constraints.length];
+	for (int i=0; i<constraints.length; i++)
+	    retval[i] = constraints[i].localName;
+	return retval;
+    } */
+
+    /**
+     * Get the "remote" column name for this relation. Uses the remote node's id as fallback if the remote field is not specified.
+     */
+    /* public String[] getRemoteFields () {
+	if (constraints == null)
+	    return new String[0];
+	String[] retval = new String[constraints.length];
+	for (int i=0; i<constraints.length; i++)
+	    retval[i] = constraints[i].foreignName;
+	return retval;
+    } */
+
+    public DbMapping getVirtualMapping () {
+	if (!virtual)
+	    return null;
+	if (virtualMapping == null) {
+	    virtualMapping = new DbMapping ();
+	    virtualMapping.subnodesRel = getVirtualSubnodeRelation ();
+	    virtualMapping.propertiesRel = getVirtualPropertyRelation ();
+	}
+	return virtualMapping;
+    }
+
+
+    /**
+     * Return a Relation that defines the subnodes of a virtual node.
+     */
+    Relation getVirtualSubnodeRelation () {
+	if (!virtual)
+	    throw new RuntimeException ("getVirtualSubnodeRelation called on non-virtual relation");
+	Relation vr = new Relation (this);
+	vr.groupby = groupby;
+	vr.groupbyorder = groupbyorder;
+	vr.groupbyprototype = groupbyprototype;
+	vr.order = order;
+	vr.filter = filter;
+	vr.constraints = constraints;
+	vr.aggressiveLoading = aggressiveLoading;
+	vr.aggressiveCaching = aggressiveCaching;
+	return vr;
+    }
+
+    /**
+     * Return a Relation that defines the properties of a virtual node.
+     */
+    Relation getVirtualPropertyRelation () {
+	if (!virtual)
+	    throw new RuntimeException ("getVirtualPropertyRelation called on non-virtual relation");
+	Relation vr = new Relation (this);
+	vr.groupby = groupby;
+	vr.groupbyorder = groupbyorder;
+	vr.groupbyprototype = groupbyprototype;
+	vr.order = order;
+	vr.filter = filter;
+	vr.constraints = constraints;
+	return vr;
+    }
+
+    /**
+     * Return a Relation that defines the subnodes of a group-by node.
+     */
+    Relation getGroupbySubnodeRelation () {
+	if (groupby == null)
+	    throw new RuntimeException ("getGroupbySubnodeRelation called on non-group-by relation");
+	Relation vr = new Relation (this);
+	vr.order = order;
+	vr.prototype = groupbyprototype;
+	vr.filter = filter;
+	vr.constraints = constraints;
+	vr.addConstraint (new Constraint (null, null, groupby, true));
+	return vr;
+    }
+
+    /**
+     * Return a Relation that defines the properties of a group-by node.
+     */
+    Relation getGroupbyPropertyRelation () {
+	if (groupby == null)
+	    throw new RuntimeException ("getGroupbyPropertyRelation called on non-group-by relation");
+	Relation vr = new Relation (this);
+	vr.order = order;
+	vr.prototype = groupbyprototype;
+	vr.filter = filter;
+	vr.constraints = constraints;
+	vr.addConstraint (new Constraint (null, null, groupby, true));
+	return vr;
+    }
+
+    public String buildWhere (INode home, INode nonvirtual, String kstr) {
+	StringBuffer q = new StringBuffer ();
+	String prefix = "";
+	if (kstr != null) {
+	    String accessColumn = accessor == null ? otherType.getIDField () : accessor;
+	    q.append (accessColumn);
+	    q.append (" = '");
+	    q.append (escape (kstr));
+	    q.append ("'");
+	    prefix = " AND ";
+	}
+	
+	for (int i=0; i<constraints.length; i++) {
+	    q.append (prefix);
+	    constraints[i].addToQuery (q, home, nonvirtual);
+	    prefix = " AND ";
+	}
+	
+	if (filter != null) {
+	    q.append (prefix);
+	    q.append (filter);
+	}
+	return q.toString ();
+    }
+
+    public String buildQuery (INode home, INode nonvirtual, String kstr) {
+	StringBuffer q = new StringBuffer ();
+	String prefix = " WHERE ";
+	if (kstr != null) {
+	    q.append (prefix);
+	    String accessColumn = accessor == null ? otherType.getIDField () : accessor;
+	    q.append (accessColumn);
+	    q.append (" = '");
+	    q.append (escape (kstr));
+	    q.append ("'");
+	    prefix = " AND ";
+	}
+	for (int i=0; i<constraints.length; i++) {
+	    q.append (prefix);
+	    constraints[i].addToQuery (q, home, nonvirtual);
+	    prefix = " AND ";
+	}
+	
+	if (filter != null) {
+	    q.append (prefix);
+	    q.append (filter);
+	}
+	if (groupby != null)
+	    q.append (" GROUP BY "+groupby);
+	if (order != null)
+	    q.append (" ORDER BY "+order);
+	return q.toString ();
+    }
+
+    /**
+     * Check if the child node fullfills the constraints defined by this relation.
+     */
+    public boolean checkConstraints (Node parent, Node child) {
+	for (int i=0; i<constraints.length; i++) {
+	    String propname = otherType.columnNameToProperty (constraints[i].foreignName);
+	    if (propname != null) {
+	        INode home = constraints[i].isGroupby ? parent : parent.getNonVirtualParent ();
+	        String localName = constraints[i].localName;
+	        String value = null;
+	        if (localName == null  || localName.equals (ownType.getIDField ()))
+	            value = home.getID ();
+	        else if (ownType.isRelational ())
+	            value = home.getString (ownType.columnNameToProperty (localName), false);
+	        else
+	            value = home.getString (localName, false);
+	        if (value != null && !value.equals (child.getString (propname, false))) {
+	            return false;
+	        }
+	    }
+	}
+	return true;
+    }
+
+
+    /**
+     * Make sure that the child node fullfills the constraints defined by this relation by setting the
+     * appropriate properties
+     */
+    public void setConstraints (Node parent, Node child) {
+	for (int i=0; i<constraints.length; i++) {
+	    String propname = otherType.columnNameToProperty (constraints[i].foreignName);
+	    if (propname != null) {
+	        INode home = constraints[i].isGroupby ? parent : parent.getNonVirtualParent ();
+	        String localName = constraints[i].localName;
+	        String value = null;
+	        if (localName == null  || localName.equals (ownType.getIDField ()))
+	            value = home.getID ();
+	        else if (ownType.isRelational ())
+	            value = home.getString (ownType.columnNameToProperty (localName), false);
+	        else
+	            value = home.getString (localName, false);
+	        if (value != null) {
+	            System.err.println ("SETTING "+child+"."+propname+" TO "+value);
+	            child.setString (propname, value);
+	        }
+	    }
+	}
+    }
+
+
+    // a utility method to escape single quotes
+    String escape (String str) {
+	if (str == null)
+	    return null;
+	if (str.indexOf ("'") < 0)
+	    return str;
+	int l = str.length();
+	StringBuffer sbuf = new StringBuffer (l + 10);
+	for (int i=0; i<l; i++) {
+	    char c = str.charAt (i);
+	    if (c == '\'')
+	        sbuf.append ("\\");
+	    sbuf.append (c);
+	}
+	return sbuf.toString ();
+    }
+
+    public String toString () {
+	String c = "";
+	if (constraints != null) {
+	    for (int i=0; i<constraints.length; i++)
+	        c += constraints[i].toString ();
+	}
+	return "Relation["+ownType+"."+propName+">"+otherType+"]" + c;
+    }
+
+    /**
+     * The Constraint class represents a part of the where clause in the query used to
+     * establish a relation between database mapped objects.
+     */
+    class Constraint {
+
+    	String localName;
+    	String tableName;
+    	String foreignName;
+    	boolean isGroupby;
+
+    	Constraint (String local, String table, String foreign, boolean groupby) {
+    	    localName = local;
+    	    tableName = table;
+    	    foreignName = foreign;
+    	    isGroupby = groupby;
+    	}
+    	
+    	public void addToQuery (StringBuffer q, INode home, INode nonvirtual) {
+    	    String local = null;
+    	    INode ref = isGroupby ? home : nonvirtual;
+    	    if (localName == null)
+    	        local = ref.getID ();
+    	    else {
+    	        String homeprop = ownType.columnNameToProperty (localName);
+    	        local = ref.getString (homeprop, false);
+    	    }
+    	    q.append (foreignName);
+    	    q.append (" = '");
+    	    q.append (escape (local));
+    	    q.append ("'");
+    	}
+    	
+    	public boolean foreignKeyIsPrimary () {
+    	    return foreignName == null || foreignName.equals (otherType.getIDField ());
+    	}
+    	
+    	public String toString () {
+    	    return ownType+"."+localName+"="+tableName+"."+foreignName;
+    	}
+    }
+
+}
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diff --git a/src/helma/objectmodel/db/SyntheticKey.java b/src/helma/objectmodel/db/SyntheticKey.java
new file mode 100644
index 00000000..86934505
--- /dev/null
+++ b/src/helma/objectmodel/db/SyntheticKey.java
@@ -0,0 +1,118 @@
+// SyntheticKey.java
+// Copyright (c) Hannes Wallnöfer 1998-2000
+ 
+package helma.objectmodel.db;
+
+import java.io.Serializable;
+
+/**
+ * This is the internal key for an object that is not - or not directly - fetched from a db,
+ * but derived from another object. This is useful for all kinds of object accessed via a
+ * symbolic name from another object, like objects mounted via a property name column,
+  * virtual nodes and groupby nodes.
+ */
+public final class SyntheticKey implements Key, Serializable {
+
+    private final Key parentKey;
+    private final String name;
+
+
+    /**
+     * make a key for a persistent Object, describing its datasource and id.
+     */
+    public SyntheticKey (Key key, String name) {
+	this.parentKey = key;
+	this.name = name;
+    }
+
+
+    public boolean equals (Object what) {
+	if (what == this)
+	    return true;
+	try {
+	    SyntheticKey k = (SyntheticKey) what;
+	    return parentKey.equals (k.parentKey) &&
+	    	(name == k.name || name.equals (k.name));
+	} catch (Exception x) {
+	    return false;
+	}
+    }
+
+    public int hashCode () {
+	return name.hashCode () + parentKey.hashCode ();
+    }
+
+
+    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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