Implicit modeling of flexible break assignments in optimal shift scheduling

The labor scheduling literature has demonstrated that the use of flexibility in designing employee schedules can result in a substantial improvement in labor utilization. This paper presents a new implicit integer linear programming formulation for the inclusion of meal/rest-break flexibility. Although the use of flexible break assignments in labor staffing decisions has been of research interest since an early article by Segal, due to problem size, the majority of related research has involved the use of heuristics. An experimental analysis using four different labor requirements patterns and ten shift-length combinations demonstrated that, when flexible break assignments were modeled, the implicit formulation was superior to the traditional set-covering formulation with respect to (1) execution time, (2) computer memory requirements, and (3) the ability to produce optimal integer solutions to larger problems incorporating greater flexibility. Finally, a number of possible extensions of the implicit modeling approach for use in other labor scheduling environments are identified.