On the conversion of decision tables to computer programs

Abstract

The use of execution time diagnostics in pinpointing ambiguities in decision tables is discussed. It is pointed out that any attempt at resolving ambiguities at compile time will, in general, be impossible. It is shown that, as a consequence, tree methods of converting decision tables to programs are inadequate in regard to ambiguity detection. Two algorithms for programming decision tables whose merits are simplicity of implementation and detection of ambiguities at execution time are presented. The first algorithm is for limited entry decision tables and clarifies the importance of proper coding of the information in the decision table. The second algorithm programs a mixed entry decision table directly without going through the intermediate step of conversion to a limited entry form, thereby resulting in storage economy. A comparison of the algorithms and others proposed in the literature is made. Some features of a decision table to FORTRAN IV translator for the IBM 7044 developed by the authors are given.