RE: Anyone can explain me this syntax?

Thanks Wendell for your complete explanation. While reading your help, I tested another alternative:

ROW[. = key('relacion_x_cobertura', REL_ID)[1]]

and it worked too. The actual XML structure has 35 ROW's, the first 7 ROW's has REL_ID = 1, the following 7 ROW's has REL_ID = 2, and so on (this was a particular case where exist 7 ROW's for each REL_ID).

I think that the new way above worked because all of the ROW's are different (besides REL_ID, the ROW has other fields), and since key('relacion_x_cobertura', REL_ID)[1] returns only 1 node where the key is equal to REL_ID, by comparing . with the key value, returns only 1 ROW, the ROW that allows me to group by REL_ID=1, REL_ID=2, until REL_ID = 5.

I think that case is equivalent to generate-id method since all ROW's has at least 1 field different, making the whole ROW different. Is that true?

Cheers,
Wendell

======================================================================
Wendell Piez                            mailto:wapiez@xxxxxxxxxxxxxxxx
Mulberry Technologies, Inc.                http://www.mulberrytech.com
17 West Jefferson Street                    Direct Phone: 301/315-9635
Suite 207                                          Phone: 301/315-9631
Rockville, MD  20850                                 Fax: 301/315-8285
----------------------------------------------------------------------
  Mulberry Technologies: A Consultancy Specializing in SGML and XML
======================================================================