2950	 A Unifying Approach to Scheduling	 This paper presents a scheme for classifying scheduling algorithms based on an abstract model of a scheduling system which formalizes the notion of priority. Various classes of scheduling algorithms are defined and related to existing algorithms. A criterion for the implementation efficiency of an algorithm is developed and results in the definition of time-invariant algorithms which include most of the commonly implemented ones. For time-invariant algorithms the dependence of processing rates on priorities is derived. The abstract model provides a framework for implementing flexible schedulers in real operating systems. The policy-driven scheduler of Bernstein and Sharp is discussed as an example of such an implementation scheduling algorithms scheduling models priority operating systems processor sharing implementation efficiency
