can you tell me which tables do i have to modify to add more fields. im also trying to change the userinfo page. i got all the web pages and the site_users sql table, but it still doesnt work. please help.

does anyone know how to modify the search in xoops. in the standard XOOPS the search has only one 'keywords' field, and i need to change that. i want to add more fields and make some of them mandatory and some of them optional. so when the user searches mandatory fields the optional ones are not required, but when the user only searches for optional fields, XOOPS doesnt let him search and tells him to fill out all the mandatory fields. please help....please.