interface Transaction { 
   exception        TransactionInProgress{}; 
   exception        TransactionNotInProgress{}; 
   void   begin()      raises (TransactionInProgress); 
   void   commit()     raises (TransactionNotInProgress); 
   void   abort()      raises (TransactionNotInProgress); 
   void   checkpoint() raises (TransactionNotInProgress); 
   void   join(); 
   void   leave(); 
   boolean  IsOpen(); 
}