Optimality of System Performance 439
1998
Maimón (1994), [6] , merges the four hierarchical levels described above into one level. The approach relys on a dynamic model essential for solving the optimiza tion problem wi th constraints, for instance by means o f the maximum principle o f Pontrjagin [7] . The above generalization supposes that the: • Machines are reliable, (i.e. that there are no machine failures).