Resource-Constrained Project Scheduling — Minimization of Project Duration

Abstract

Thus far, we have not taken account of the limited availability of resources which are required for carrying out the activities of a project. In what follows, we are going to take scarce resources into consideration. In practice, different types of resources may occur. Renewable resources (such as machines, equipment, or manpower) are available at each point in time or, if time is discrete, in each single time period during the execution of the project independently of their utilization formerly. Nonrenewable resources (e.g. money or energy) are depleted by use. Nonrenewable resources only affect the scheduling of activities if activities can be carried out in alternative modes which differ, for example, in duration and amount of resources needed. We then speak of multi-mode project scheduling problems in contrast to single-mode problems. Cumulative resources represent storage facilities. They can store a single or several different products and have a prescribed minimum and maximum inventory, where the inventory is generally depleted and replenished over time. Additional resource types, like partially renewable resources (cf. Böttcher et al., 1999), whose capacity refers to sets of time periods, have been discussed in literature.