The sequencing problem of one machine with limited conditions

A directed graph D with n vertices is defined according to the sequence of n given spare parts that are processed on one machine. When the graph D is simplified, a sequencing graph D* is obtained. By wholly enumerating the topological sequence of vertices of graph D*, we can find the processing sequence that minimises the sum of the times that the n spare parts take to complete processing, the time that the machine requires to complete n spare parts is the least and the loss because the delay is the least.