What are single-dimension scheduling rules? Provide examples and discuss how each rule performs

Question

What will be an ideal response?

Answer 1

Single-dimension rules (e.g., FCFS, EDD, and SPT) base a job's priority assignment on a single aspect of the job, such as arrival time at the workstation, the due date, or the processing time. Studies have found that the EDD rule performs well with respect to the percentage of jobs past due and the variance of hours past due. For any set of jobs to be processed at a single workstation, it minimizes the maximum of the past due hours of any job in the set. Often referred to as the world champion, the SPT rule tends to minimize the mean flow time (assuming time since arrival is 0 for all jobs) and the percentage of jobs past due. It also tends to maximize shop utilization. For the single-workstation case, the SPT rule always will provide the lowest mean finish time. However, it could increase total inventory because it tends to push all work to the finished state. In addition, it tends to produce a large variance in past due hours because the larger jobs might have to wait a long time for processing. Also, it provides no opportunity to adjust schedules when due dates change. Finally, though the FCFS rule is considered fair to the jobs (or customers), it performs poorly with respect to all performance measures. However, FCFS usually is the only acceptable choice for service processes where the customer is present and demand leveling options such as appointments or reservations are not used.