As used in this article, unless the context otherwise requires:
(1) "Cooperative purchasing" means procurement conducted by, or on behalf of, more than one public procurement unit or by a public procurement unit with an external procurement activity.
(2) "External procurement activity" means any buying organization not located in this state which, if located in this state, would qualify as a public procurement unit. An agency of the United States is an external procurement activity.
(3) "Local public procurement unit" means any county, city, county and city, municipality, or other political subdivision of the state, any public agency of any such political subdivision, any public authority, any educational, health, or other institution, and, to the extent provided by law, any other entity which expends public funds for the procurement of supplies, services, and construction.
(4) "Public procurement unit" means either a local public procurement unit or a state public procurement unit.
(5) "State public procurement unit" means the department of personnel or any other purchasing agency of this state.
Any public procurement unit may either participate in, sponsor, conduct, or administer a cooperative purchasing agreement for the procurement of any supplies, services, or construction with one or more public procurement units, external procurement activities, or procurement consortiums which include as members tax-exempt organizations as defined by section 501 (c)(3) of the federal "Internal Revenue Code of 1986", as amended, in accordance with an agreement entered into between the participants. Such cooperative purchasing may include, but is not limited to, joint or multiparty contracts between public procurement units and open-ended state public procurement unit contracts which are made available to local public procurement units.