Advanced Concepts in Systems Design

This chapter focuses on a number of issues that have come up in recent years in the design, development, and implementation of planning and scheduling systems. The next section discusses issues concerning uncertainty, robustness and reactive decision making. In practice, plans or schedules often have to be changed because of random events. The more robust the original plan or schedule is, the easier the replanning or rescheduling process is. This section focuses on the generation of robust plans and schedules as well as the measurement of their robustness. The third section considers machine learning mechanisms. A system cannot consistently generate good solutions that are to the liking of the user. The decision-maker often has to tweak the plan or schedule generated by the system in order to make it usable. A well-designed system can learn from adjustments made by the user in the past; the mechanism that allows the system to do so is typically referred to as a learning mechanism. The fourth section focuses on the design of planning and scheduling engines. An engine often contains a library of algorithms and routines. One procedure may be more appropriate for one type of instance or data set, while another procedure may be more appropriate for another type of instance. The user should be able to select, for each instance, which procedure to apply. It may even be the case that a user would like to tackle an instance using a combination of various procedures. This fourth section discusses how a planning or scheduling engine should be designed in order to enable the user to adapt and combine algorithms in order to achieve maximum effectiveness. The fifth section focuses on reconfigurable systems. Experience has shown that the development and implementation of systems is very time consuming and costly. In order to reduce the costs, efforts should be made to maintain a high degree of modularity in the design of the system. If the modules are well designed and sufficiently flexible, they can be used over and over again without any major changes. The sixth section focuses on the design aspects of web-based planning and scheduling systems. This section discusses the effects of networking on the design of such systems. The seventh and last section discusses a number of other issues and presents a view on how planning and scheduling systems may evolve in the future.