An updated survey of variants and extensions of the resource-constrained project scheduling problem *

The resource-constrained project scheduling problem is to schedule activities subject to precedence and resource constraints such that the makespan is minimized. It has become a standard problem in the context of project scheduling which has attracted numerous researchers who developed both exact and heuristic scheduling procedures. However, it is a rather stylized model with assumptions that are too narrow to capture many real world requirements. Consequently, various extensions of the basic resource constrained project scheduling problem have been developed. This paper builds on an overview which was published 10 years ago. Due to the unabated interest in the scientific community since it has been published the overview at hand delivers an update focussing on the last decade. The problem extensions are classified according to the structure of the resource-constrained project scheduling problem. We summarize generalizations of the activity concept, of the precedence relations, and of the resource constraints. Alternative objectives and approaches for scheduling multiple projects are discussed as well. (c) 2021 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license ( http://creativecommons.org/licenses/by-nc-nd/4.0/ )