SQL documentation

I'm trying a technique I found on the web, and I'd like to see the manual on it but I'll be darned if I can figure out which one has it. First, the technique from http://www.ibm.com/developerworks/db2/library/techarticle/0307balani/0307balani.html

SELECT * FROM (
SELECT PRODUCT_ID, PRODUCT_NAME,
PRODUCT_DESCRIPTION, PRODUCT_PRICE,
rownumber() OVER
(ORDER BY PRODUCT_ID) AS ROW_NEXT
FROM PRODUCT,PRODUCT_CATEGORY
WHERE
PRODUCT. PROD_CATEGORY_ID
= PRODUCT_CATEGORY.CATEGORY_ID
AND
PRODUCT_CATEGORY.CATEGORY_ID = 'Books'
AND
PRODUCT. PRODUCT_DESCRIPTION LIKE
'Application Servers'
)
AS PRODUCT_TEMP WHERE
ROW_NEXT BETWEEN ? and ?

This works in DB2 UDB for i5/OS V5R4. What I'm trying to work out is where I can find the documentation for this, specifically the SELECT ... AS PRODUCT_TEMP.

I looked in the SQL Reference and the Programming guide. I'm guessing it's related to the OLAP [ROW_NUMBER or rowid()] which I see in the Reference examples, but not in the syntax diagrams.
--buck