Example 1 of Variable Elimination
XD(a,i,r,t) = # of type a aircraft direct delivering cargo for customer i on route r departing at time t
Allow variable to exist only if
Route r is a direct delivery route from customer i ’s origin to i ’s destination
Aircraft type a is available at i ’s origin at t
Aircraft type a can fly route r ’s critical leg
Aircraft type a can carry some cargo type that customer i demands
Time t is not before i ’s available-to-load time
Time t is not after i ’s required delivery date + maxlate – travel time