Some models are:
Institutional model
It focuses on the traditional organization of government and describes the duties and arrangements of bureaus and departments. It considers constitutional provisions, administrative and common law, and judicial decisions. It focuses on formal arrangements such as federalism executive reorganizations, presidential commission, etc. Traditionally political science has studied government institutions--Congress, presidency, courts, political parties, etc.--that authoritatively determine, implement, and enforce public policy. Strictly speaking, a policy is not a public policy until it is adopted, implemented and enforced by some governmental institution. Government lends legitimacy to policies, they are then legal; Government extends policies universally to cover all people in society; Government monopolizes the power to coerce obedience to policy, or to sanction violators. Traditional studies using the institutional approach focused on institutional structures, organization, duties and function, without investigating their impact on public policy.
Process model
Policy creation is a process following these steps: * Identification of a problem and demand for government action. * Formulation of policy proposals by various parties (e.g., congressional committees, think tanks, interest groups). * Selection and enactment of policy; this is known as Policy Legitimating. * Implementation of the chosen policy. * Evaluation of policy.
This model, however, has been criticized for being overly linear and simplistic. In reality, stages of the policy process may overlap or never happen. Also, this model fails to take into account the multiple actors attempting to influence the process itself as well as each other,