Conversion of Limited-Entry Decision Tables to Computer Programs

by Solomon L. Pollack

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Decision tables are useful for describing a set of complex decision rules based on given sets of conditions. Algorithms that can efficiently convert the tables into computer programs will extend the usefulness of decision tables to computer users. This memorandum describes two such algorithms, based on work done by M. S. Montalbano and extended here to handle dashes and ELSE-decision rules. The first algorithm minimizes the computer storage space; the second minimizes computer running time. During the conversion process, both pinpoint any contradictions or redundancies among the rules in a table. A necessary adjunct to minimizing computer storage or running time is the allowable reduction of the number of rules in a decision table. This memorandum describes a technique for this reduction for pairs, triplets, and quadruplets of rules. The system analyst will find this method most helpful for pairs, and generally unprofitable for n-tuplets greater than three. The technique is used manually or by the computer as a prelude to executing one of the two algorithms. Decision tables are useful for describing a set of complex decision rules based on given sets of conditions. Algorithms that can efficiently convert the tables into computer programs will extend the usefulness of decision tables to computer users. This memorandum describes two such algorithms, based on work done by M. S. Montalbano and extended here to handle dashes and ELSE-decision rules. The first algorithm minimizes the computer storage space; the second minimizes computer running time. During the conversion process, both pinpoint any contradictions or redundancies among the rules in a table. A necessary adjunct to minimizing computer storage or running time is the allowable reduction of the number of rules in a decision table. This memorandum describes a technique for this reduction for pairs, triplets, and quadruplets of rules. The system analyst will find this method most helpful for pairs, and generally unprofitable for n-tuplets greater than three. The technique is used manually or by the computer as a prelude to executing one of the two algorithms. (See also RM-3010, RM-3669, P-2829.)

This report is part of the RAND Corporation research memorandum series. The Research Memorandum was a product of the RAND Corporation from 1948 to 1973 that represented working papers meant to report current results of RAND research to appropriate audiences.

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