Index sets

declarations
  MaxCap: array(1..10) of linctr
end-declarations

forall(d in 1..10)
  MaxCap(d) :=
    sum(p in 1..10, m in 1..10)
      TECH(p,m,d)*x(p,m,d) <= MAXTECH(d)

declarations
  PRODUCTS = 1..5
  MATERIALS = {12,487,163}
  DEPOTS = {"Boston","New York","Atlanta"}

  MaxCap: array(DEPOTS) of linctr
end-declarations

forall(d in DEPOTS)
  MaxCap(d) :=
    sum(p in PRODUCTS, m in MATERIALS)
      TECH(p,m,d)*x(p,m,d) <= MAXTECH(d)

• improves the readability of a model
• makes it easier to apply the model to different sized data sets
• makes the model easier to maintain