1. For the purposes of this Regulation, the following definitions shall apply:

(a) "central liaison office" means the office which has been designated pursuant to Article 4(1) with principal responsibility for contacts with other Member States in the field of administrative cooperation;

(b) "liaison department" means any office other than the central liaison office which has been designated as such by the competent authority pursuant to Article 4(2) to exchange directly information on the basis of this Regulation;

(c) "competent official" means any official who can directly exchange information on the basis of this Regulation for which he has been authorised pursuant to Article 4(3);

(d) "requesting authority" means the central liaison office, a liaison department or any competent official of a Member State who makes a request for assistance on behalf of the competent authority;