Question regarding model clause

Hi,

Damorgan is right. If you want a solution that works in your version, why not say what your version is?
Always explain what you're trying to do. Posting the results from your sample data, like you did, is great, but there's always a chance someone will give you a solution that happens to work perfectly on your sample data, but won;t work on your real data. Guessing is not a very efficient way to work. Don't make people guess what you want.

To get the results you requested, you don't need MODEL at all;

SELECT	rnk
,	(3 * rnk) - 2	AS first
,	(3 * rnk)	AS second
FROM	(
        SELECT	1 	AS rnk FROM dual
        UNION ALL
        SELECT	2 	AS rnk FROM dual
	)
;

If you really want to use MODEL, then make a special case for SECOND[1], like you did for FIRST[1].
Also, use AUTOMATIC ORDER, since there are dependencies among the rules

SELECT  RNK,
        FIRST,
        SECOND
FROM    (
        SELECT 1 RNK FROM DUAL
        UNION ALL
        SELECT 4 RNK FROM DUAL
        UNION ALL
        SELECT 2 RNK FROM DUAL
)
MODEL
DIMENSION BY ( RNK )
MEASURES ( 
        	0 FIRST, 
        	0 SECOND
	 )
RULES 	AUTOMATIC ORDER
      (
        FIRST [1] = 1,
	SECOND[1] = 3,
        FIRST [RNK > 1] = SECOND[CV(RNK) - 1] + 1,
        SECOND[RNK > 1] = FIRST[CV()] + 2
      )
;

or just intialze row 1 the way you want it:

SELECT  RNK,
        FIRST,
        SECOND
FROM    (
        SELECT 1 RNK FROM DUAL
        UNION ALL
        SELECT 2 RNK FROM DUAL
        UNION ALL
        SELECT 3 RNK FROM DUAL
)
MODEL
DIMENSION BY ( RNK )
MEASURES ( 
        	1 FIRST, 
        	3 SECOND
	 )
RULES 	AUTOMATIC ORDER
      (
        FIRST [RNK > 1] = SECOND[CV(RNK) - 1] + 1,
        SECOND[RNK > 1] = FIRST[CV()] + 2
      )
;