H. Brasel et al., A POLYNOMIAL ALGORITHM FOR AN OPEN SHOP PROBLEM WITH UNIT PROCESSING TIMES AND TREE CONSTRAINTS, Discrete applied mathematics, 59(1), 1995, pp. 11-21
In this paper we consider the open shop problem with unit processing t
imes and tree constraints (outtree) between the jobs. The complexity o
f this problem was open. We present a polynomial algorithm which decom
poses the problem into subproblems by means of the occurrence of unavo
idable idle time. Each subproblem can be solved on the base of an algo
rithm for the corresponding open shop problem without tree constraints
.