Using multiobjective program or linear objective integer program
to set up P disposal nodes in order to minimize the total
distance between demands and disposal nodes, e.g., Church and
Velle (1974) proposed that the efficiency of a disposal node is determined
by the average distance from the demand to this very node;
ReVelle refined the P-center model to either maximize the number
of customers a disposal node could handle or maximize profits. This
model is applicable to integer program or moderate-scaled locating
cases.