Disjunctive constraints for manufacturing scheduling: principles and extensions

Disjunctive constraints are widely used to ensure that the time intervals over which two activities require the same resource do not overlap in time. Two types of extensions of disjunctive constraints are proposed: (1) extensions allowing the representation of more complex constraints including activities that may or may not require the resource, ‘state resources’ to represent activities which may use resources only under specific conditions, and a mechanism to represent setup times between activities; (2) extensions of the disjunctive constraint propagation algorithm to deduce more precise time-bounds. These extensions are integrated in ILOG SCHEDULE, a C++library for constraint-based scheduling.