In serial production systems, storage may be provided between processes to avoid interference due to lack of synchronization. This paper investigates the behavior of lines buffered in this way and explores the distribution and quantity of work-in-process (WIP) inventory that accumulates. We study simple, generic production systems to gain insight into the behavior of more complex systems. The authors are surprised by the sometimes counterintuitive results, but are joined in this surprise by both academics and practitioners with whom the study has been discussed. Results are presented for: identical workstations with and without buffers; balanced lines in which variability of processing times differs between stations; unbalanced lines; and lines with unreliable workstations. In general, buffers between workstations increase system capacity but with sharply diminishing returns. Position as well as capacity of the buffers are important. These results are preliminary, to be confirmed and extended by further study—indeed, a primary purpose of this paper is to stimulate such study. However, even these preliminary results yield design guidelines that should be useful in industrial practice.

This paper is concerned with the manner in which an investigation by simulated experimentation is conducted, after the model has been formulated and the computer program completed. It considers the problem of estimating the precision of the results obtained, and methods of improving the precision of results. Alternative procedures are discussed and recommendations are given.

SCHNEIDERInteractive systems, such as editors and program development environments, should explicitly support facilities that permit a user to reverse the effects of past actions and to restore an object to a prior state. A model for interactive systems that allows such recovery facilities to be defined precisely and user and system responsibilities to be delineated is presented. Various techniques for implementing recovery are described. Application of a general recovery facility to support reverse execution is discussed. A program development system (called COPE} with extensive recovery facilities, including reverse execution, is described.

The significance of the dispatching function in production planning and control is discussed and applicable results in sequencing and queuing theory are reviewed. Experimental results for a network of queues representing a small job shop are presented. The investigation involved the comparison of dispatching at random with dispatching in order of increasing processing time under different conditions of shop size, flow pattern, and level of work-in-process inventory. Also considered is the effect of imperfect a priori knowledge of processing times upon the shortest-operation discipline Several modifications of the shortest-operation discipline were also tested one in which the shortest-operation discipline is ‘truncated’ and another in which it is periodically alternated with a first-come-first-served discipline.