* Corresponding author. E-mail address: paultu@ucalgary.ca (Y. Tu) © 2020 by the authors; licensee Growing Science, Canada doi: 10.5267/j.jpm.2019.11.001 Journal of Project Management 5 (2020) 117–138 Contents lists available at GrowingScience Journal of Project Management homepage: www.GrowingScience.com A survey in the resource-constrained project and multi-project scheduling problems Samer Ben Issa a and Yiliu Tu a* a Schulich School of Engineering, Department of Mechanical and Manufacturing Engineering, University of Calgary, Canada C H R O N I C L E A B S T R A C T Article history: Received: September 20 2019 Received in revised format: Oc- tober 2 2019 Accepted: November 14 2019 Available online: November 14 2019 Resource-Constrained Project and Multi-Project Scheduling Problems (RCPSPs and RCMPSPs) have been essential topics of study over the last three decades. Both problems consist of activities that must be scheduled subject to precedence and resource constraints. This paper surveys studies of RCPSPs and RCMPSPs under consideration of four categories of project activities, simply recorded as categories A, B, C, and D. Category A refers to activities can be performed using fixed resources along The Y-axis over fixed durations along The X-axis, and cannot be interrupted. Category B applies to activities that can be performed using the same type of resource in category A but can be interrupted. Category C refers to activities that can be performed using flexible resources over flexible durations and cannot be interrupted. Category D refers to activities can be performed using flexible re- sources over flexible durations and can be interrupted. Many algorithms have been devel- oped to solve the RCPSPs and RCMPSPs when activities are classified individually under category A, B, or C. However, in practice, welding, cutting or assembly activities in a man- ufacturing projects for an oil cargo can be under a new category so-called D. The project manager can speed up or slow down these activities by allocating or removing more re- sources, and these activities can be interrupted or can be resumed at any time. From the perspective of activity categories, we intend to review the literature on RCPSPs and RCMP- SPs and to obtain the new research directions for solving the problems. © 2020 by the authors; licensee Growing Science, Canada. Keywords: Project scheduling ABCD activity classifications Limited resources 1. Introduction In this section, Table 1 shows the entire notations used in the study. Table 1 The entire notations used in this study. A-O-A Activity-On-Arc A-O-N Activity-On-Node B&B Branch and Bound BCO Bee Colony Optimization BFI Backward-Forward Improvement. BPGA Bi-Population Genetic Algorithm.