ABSTRACT
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).
