4D relationships: The missing link in 4D scheduling

Four-dimensional (4D) schedules have proven successful in planning with their visualization capabilities allowing for coordination and time-space conflict detection. However, when considered in depth, internal aspects of 4D scheduling techniques have not made significant advances from traditional two-dimensional (2D) scheduling. What is missing from 4D scheduling? Why has the interaction between activities, their relationships, and three-dimensional (3D) components not been flexible and adaptive enough? In light of these questions, this paper analyzes the current state of 4D scheduling. The missing element in 4D scheduling is found to be 4D relationships (4DRs). A prototype of 4DRs has therefore been developed to improve 4D scheduling. Finally, guidance on the application of 4DRs in 4D scheduling is presented to help the users come to a thorough understanding of its advantages and disadvantages and potential applications.