The Meyers-Milias-Brown Act (MMBA) has two stated purposes. One is "to promote the improvement of personnel management and employer-employee relations within the various public agencies in the State of California by providing a uniform basis for recognizing the right of public employees to join organizations of their own choice and be represented by such organizations in their employment relationships with public agencies." ( 3500.) Public employees are given "the right to form, join, and participate in the activities of employee organizations of their own choosing for the purpose of representation on all matters of employer-employee relations." ( 3502.) Public employees may select an "employee organization" to represent them "in their employment relations with public agencies" ( 3503) and may negotiate an "agency shop agreement" with public agencies. ( 3502.5.) Public employees are also given the right not to join an employee organization if they prefer to represent themselves individually. ( 3502.) The second purpose of the MMBA is "to promote full communication between public employers and their employees by providing a reasonable method of resolving disputes regarding wages, hours, and other terms and conditions of employment between public employers and public employee organizations." ( 3500.) The scope of representation of public employees by an employee organization extends to these issues. ( 3504.) Employee organizations must be given written notice of action "directly relating to matters within the scope of representation" ( 3504.5) and must "meet and confer in good faith" regarding matters within the scope of representation. ( 3505.) If agreement is reached, it must be reduced to a "memorandum of such understanding." ( 3505.1.) The MMBA was not intended to occupy the field and preempt local regulation. "Nothing contained herein shall be deemed to supersede the . . . rules of local public agencies which establish and regulate a merit or civil service system or which provide for other methods of administering employer-employee relations" ( 3500). Looking to the future, the MMBA authorizes public agencies to adopt "reasonable rules and regulations" on specified subjects after meeting and conferring with employee organizations. ( 3507.) One of those subjects is "additional procedures for the resolution of disputes involving wages, hours and other terms and conditions of employment" (id., subd. (e)). The MMBA deals with a matter of statewide concern, and its standards may not be undercut by contradictory rules or procedures that would frustrate its purposes. (E.g., Voters for Responsible Retirement v. Board of Supervisors (1994) 8 Cal. 4th 765, 781 [35 Cal. Rptr. 2d 814, 884 P.2d 645]; International Brotherhood of Electrical Workers v. City of Gridley (1983) 34 Cal. 3d 191, 197-198 [193 Cal. Rptr. 518, 666 P.2d 960]; San Bernardino County Sheriff's etc. Assn. v. Board of Supervisors (1992) 7 Cal. App. 4th 602, 613 [8 Cal. Rptr. 2d 658].) Local regulation is permitted only if "consistent with the purposes of the MMBA." (Los Angeles County Civil Service Com. v. Superior Court (1978) 23 Cal. 3d 55, 63 [151 Cal. Rptr. 547, 588 P.2d 249].) The essential predicate for effective operation of the MMBA is the unit into which public employees are organized and represented by an employee organization. (See Grodin, Public Employee Bargaining in California: the Meyers-Milias-Brown Act in the Courts (1972) 23 Hastings L.J. 719, 738.) There is only one express statutory qualification: the unit must be "appropriate." ( 3507, subd. (d), 3507.1.) the first attempt at assaying the criteria for determining whether a unit is "appropriate" was made by this court in 1973 when a group of assistant public defenders objected to their assignment to a bargaining unit composed of all non-health-related professionals. Analogizing from federal precedent under the National Labor Relations Act (29 U.S.C. 151 et seq.), we recognized that unit determinations made by public agencies would not be overturned if they were "reasonable." With respect to the standard for determining reasonableness, we adopted the "community of interest" test and applied it to a group of professional employees. Taking account of such factors as the " 'distinct nature of their function, their separate supervision and work place, the lack of substantial interchange with other professional employees, and the fact that they are separately hired,' " we held that the attorneys were "sui generis" and therefore entitled to form a separate bargaining unit. (Alameda County Assistant Public Defenders Assn. v. County of Alameda (1973) 33 Cal. App. 3d 825, 830-832 [109 Cal. Rptr. 392], quoting Douglas Aircraft Co. (1966) 157 NLRB 68; see 29 U.S.C. 159(b).) Our approach has subsequently been adopted by other courts. (See Reinbold v. City of Santa Monica (1976) 63 Cal. App. 3d 433, 440 [133 Cal. Rptr. 874] and decisions cited.)