(a) A party may appear in person or by counsel or other representative and participate fully in any proceedings. An agency, state or local body, corporation or other association, may appear by any of its officers or by any employee it authorizes to appear on its behalf.

(b) A representative of a party or participant shall be deemed to control all matters respecting the interest of such party or participant in the proceedings.

(c) This section shall not be construed to require any representative to be an attorney-at-law.

(d) Withdrawal of appearance of any representative is effective when a written notice of withdrawal is filed and served on all parties and participants.