Comments on "A practical approach to job shop scheduling problems" [with reply]

The author states that, in the original paper (D.L. Hoitomt and P.B. Luh ibid., vol. 9, no. 1, p. 1-13, 1993), the model formulation of the scheduling problem is highly irregular. If one were to consider the formulation by itself it would seem that since neither the precedence nor processing time constraints are linked to time, we could set all /spl delta//sub ijkh/=0 and obtain a feasible solution with jobs overlapping on machines. It is noted that in the subsequent relaxation of the capacity constraint, the binary variables have been set to 1 from start to finish time of the corresponding operation to account for capacity. The need for the model formulation to include such constraints explicitly is discussed, and the original authors discuss the relevance of the comments. The existence of related and similar results in previous works is also considered.<>