For purposes of challenging the contents of an agency's commercial activities inventory pursuant to the Federal Activities Inventory Reform Act, an interested party is (1) a private sector source that is an actual or prospective offeror for a contract or other form of agreement to perform the activity and has a direct economic interest in performing the activity that would be adversely affected by a determination not to procure the performance of the activity from a private sector source; (2) a representative of any business or professional association that includes within its membership private sector sources referred to in (1) above; (3) an officer or employee of an organization within an executive agency that is an actual or prospective offeror to perform the activity; (4) the head of any labor organization referred to in section 7103(a)(4) of title 5, United States Code, that includes within its membership officers or employees of an organization referred to in paragraph (3).