In the case of point NF and point EFs, if one starts with a location of objective function value
z, then the slope in the cell to which X belongs will cause the contour line to be incident on some
adjacent cells and the process can be repeated until the contour is closed. In our case, the contour
line and set for a particular value z can only be constructed after evaluating all the cells, at least
implicitly, to identify those cells which contain an X such that f(X) = z. We start the implicit
enumeration by eliminating certain cells and thus identify a set of candidate cells Sz which potentially
contain an X such that f(X) = z. The NF may interfere with the material flow in some cells while
in others it may not. In those cells where the NF interferes with the flow it does so only in the region
Q associated with the affected traversal path. Therefore the set Sz may be classified as shown in
Fig. 8. In our analysis, we consider the objective function and the method to calculate the slope
of the contour line in each of them separately. We start by illustrating our methodology through a
numerical example where an NF has to be placed in a shop floor having two EF I/O points, i and j.
The weights of the flow between facilities are as shown in Fig. 9. We then present a general procedure
to construct the contour line for a given problem instance.