The spatial analysis has the advantage that the relation between the cases and attributes is explicit. Figure 22 Setting the type of each quality Running the Induct logical entailment analyis program then produces the rules shown in Figure 23. These conclude that soft lenses should be fitted when tear production is normal and the astigmatism is not astigmatic, and that hard lenses should be fitted when tear production is normal and the astigmatism is astigmatic. Note that this is already the simple default rule set for the contact lens situation already discussed. The exception rules are missing because the expert has not yet entered clients that should not have lenses fitted for other reasons.
Several possibilities are open.
It does not really matter what prompts the expert to remember that age and prescription are also relevant variables and that there are some special cases that should be entered. Note that it also does not matter if the expert enters a duplicate case. It will affect the result if the expert enters an incorrect decision. If this conflicts with an existing case it will be noticed quickly. Otherwise, it will be apparent through studying the graphic representations or rules.