Default attribute items have numeric item-IDs starting with 1. These item-IDs are used by AQL sentences as output specifications if no other output specifications are given. The numeric item-IDs must be consecutive; that is, in order to have the third attribute list by default, attribute items 1 and 2 must exist, even if they are not needed for the listing. The attribute items for attributes that are not needed for listings can be given a dictionary code of x.