-# ALGO :
-# this script use an $op to know what to do.
-# if $op is empty or none of the above values,
-# - the default screen is build (with all records, or filtered datas).
-# - the user can clic on add, modify or delete record.
-# if $op=add_form
-# - if primkey exists, this is a modification,so we read the $primkey record
-# - builds the add/modify form
-# if $op=add_validate
-# - the user has just send datas, so we create/modify the record
-# if $op=delete_form
-# - we show the record having primkey=$primkey and ask for deletion validation form
-# if $op=delete_confirm
-# - we delete the record having primkey=$primkey
-
-