Is 'changed' mandatory for a network object?

Hi everybody, i'd like to know if the 'changed' attribute for the network object is mandatory. RIPE-50.txt does not say anything. and the DB software configuration file says it's mandatory. Thanks, Laurent -- Laurent Joncheray, E-Mail: lpj@merit.edu Merit Network Inc, 1071 Beal Avenue, Phone: +1 (313) 936 2065 Ann Arbor, MI 48109, USA Fax: +1 (313) 747 3745 "This is the end, Beautiful friend. This is the end, My only friend, the end" JM