Further Results on the Problem of Finding Minimal Length Programs for Decision Tables

Abstract

In this paper it is shown that whatever the length function employed, the problem of finding the shortest program for a decision table with two (or more) entries is not recursively solvable (whereas for decision tables with a single entry the problem is solvable for some length functions and unsolvable for others). Moreover, it is shown that there is a pair of finite sets of programs and a single entry E such that the shortest program for the decision table formed by adding a single additional entry to E is in all cases in one of the two sets, but it is undecidable in which. Some consequences of these results are then presented, such as showing that for a wide range of restrictions the results remain true, even when the repertoire of possible programs for a decision table is narrowed by only considering programs which meet certain restrictions.