public DataCollection retrieve(String typeName) { return retrieve(m_root.getObjectType(typeName));
public DataObject retrieve(OID oid) { Map props = oid.getProperties(); if (props.size() == 1) { return (DataObject) m_ssn.retrieve (C.type(oid.getObjectType()), props.values().iterator().next()); } else { throw new Error("not implemented"); }
    public DataCollection retrieve(String typeName) {        return retrieve(m_root.getObjectType(typeName));    }