In term of design problems. the unique answer for a given problem does not
generally exist since an individual makes decision, which is selective, cumulative,
and tentative, and this is contradictory to optimization problem (Simon 1975). In
solving optimization problems, the derived answers are well defined and they are
optimized to chosen criteria (Heragu 1997). Regarding to the characteristic of
plant layout problem, plant layout problem should not be considered as neither
pure design problem nor pure optimization problem (Heragu 1997). This is
because there are many factors involved both qualitative factors and quantitative