if ( transStack.empty( ) ) { sendNotifcations( new ActivityStackEvent( this, ActivityStackEvent.ROLL_BACK ) ); }
	public void rollback( )	{		assert transStack.size( ) > 0;		CompoundRecord trans = (CompoundRecord) transStack.pop( );		// silent task do not perform tasks here since values on elements		// are not changed.		trans.rollback( );		trans.destroy( );	}