SQL & PL/SQL

Hi,

Does anyone know how to implement the Singleton design pattern in PL/SQL? I'm afraid I knowledge of PL/SQL is somewhat limited. The UDT I want to apply the design pattern to is outlined below: -

CREATE OR REPLACE TYPE VALIDATED_DATA_ARRAY AS OBJECT
(
g_table_names VARCHARARRAY,
g_column_names VARCHARARRAY,

CONSTRUCTOR FUNCTION VALIDATED_DATA_ARRAY RETURN
SELF AS RESULT,

MEMBER PROCEDURE setValidatedData
( a_table_name VARCHAR2, a_column_name VARCHAR2 ),
MEMBER FUNCTION getColumnName
( a_table_name VARCHAR2 ) RETURN VARCHAR2
);
/

Regards,

Sean