SAINT (Inventions)

The invention: Taking its name from the acronym for symbolic automatic integrator, SAINT is recognized as the first “expert system”—a computer program designed to perform mental tasks requiring human expertise.

The person behind the invention:

James R. Slagle (1934-1994), an American computer scientist

The Advent of Artificial Intelligence

In 1944, the Harvard-IBM Mark I was completed. This was an electromechanical (that is, not fully electronic) digital computer that was operated by means of coding instructions punched into paper tape. The machine took about six seconds to perform a multiplication operation, twelve for a division operation. In the following year, 1945, the world’s first fully electronic digital computer, the Electronic Numerical Integrator and Calculator (ENIAC), became operational. This machine, which was constructed at the University of Pennsylvania, was thirty meters long, three meters high, and one meter deep.
At the same time that these machines were being built, a similar machine was being constructed in the United Kingdom: the automated computing engine (ACE). Akey figure in the British development was Alan Turing, a mathematician who had used computers to break German codes during World War II. After the war, Turing became interested in the area of “computing machinery and intelligence.” He posed the question “Can machines think?” and set the following problem, which is known as the “Turing test.” This test involves an interrogator who sits at a computer terminal and asks questions on the terminal about a subject for which he or she seeks intelligent answers. The interrogator does not know, however, whether the system is linked to a human or if the responses are, in fact, generated by a program that is acting intelligently. If the interrogator cannot tell the difference between the human operator and the computer system, then the system is said to have passed the Turing test and has exhibited intelligent behavior.

SAINT: An Expert System

In the attempt to answer Turing’s question and create machines that could pass the Turing test, researchers investigated techniques for performing tasks that were considered to require expert levels of knowledge. These tasks included games such as checkers, chess, and poker. These games were chosen because the total possible number of variations in each game was very large. This led the researchers to several interesting questions for study. How do experts make a decision in a particular set of circumstances? How can a problem such as a game of chess be represented in terms of a computer program? Is it possible to know why the system chose a particular solution?
One researcher, James R. Slagle at the Massachusetts Institute of Technology, chose to develop a program that would be able to solve elementary symbolic integration problems (involving the manipulation of integrals in calculus) at the level of a good college freshman. The program that Slagle constructed was known as SAINT, an acronym for symbolic automatic integrator, and it is acknowledged as the first “expert system.”
An expert system is a system that performs at the level of a human expert. An expert system has three basic components: a knowledge base, in which domain-specific information is held (for example, rules on how best to perform certain types of integration problems); an inference engine, which decides how to break down a given problem utilizing the rules in the knowledge base; and a human-computer interface that inputs data—in this case, the integral to be solved—and outputs the result of performing the integration. Another feature of expert systems is their ability to explain their reasoning.
The integration problems that could be solved by SAINT were in the form of elementary integral functions. SAINT could perform indefinite integration (also called “antidifferentiation”) on these functions. In addition, it was capable of performing definite and indefinite integration on trivial extensions of indefinite integration. SAINT was tested on a set of eighty-six problems, fifty-four of which were drawn from the MIT final examinations in freshman calculus; it succeeded in solving all but two. Slagle added more rules to the knowledge base so that problems of the type it encountered but could not solve could be solved in the future.
Basic structure of an expert system.
Basic structure of an expert system.
The power of the SAINT system was, in part, based on its ability to perform integration through the adoption of a “heuristic” processing system. Aheuristic method is one that helps in discovering a problem’s solution by making plausible but feasible guesses about the best strategy to apply next to the current problem situation. A heuristic is a rule of thumb that makes it possible to take short cuts in reaching a solution, rather than having to go through every step in a solution path. These heuristic rules are contained in the knowledge base. SAINT was written in the LISP programming language and ran on an IBM 7090 computer. The program and research were Slagle’s doctoral dissertation.


The SAINT system that Slagle developed was significant for several reasons: First, it was the first serious attempt at producing a program that could come close to passing the Turing test. Second, it brought the idea of representing an expert’s knowledge in a computer program together with strategies for solving complex and difficult problems in an area that previously required human expertise. Third, it identified the area of knowledge-based systems and

James R. Slagle

James R. Slagle was born in 1934 in Brooklyn, New York, and attended nearby St. John’s University. He majored in mathematics and graduated with a bachelor of science degree in 1955, also winning the highest scholastic average award. While earning his master’s degree (1957) and doctorate (1961) at the Massachusetts Institute of Technology (MIT), he was a staff mathematician in the university’s Lincoln Laboratory.
Slagle taught in MIT’s electrical engineering department part-time after completing his dissertation on the first expert computer system and then moved to Lawrence-Livermore National Laboratory near Berkeley, California. While working there he also taught at the University of California. From 1967 until 1974 he was an adjunct member of the computer science faculty of Johns Hopkins University in Baltimore, Maryland, and then was appointed chief of the computer science laboratory at the Naval Research Laboratory (NRL) in Washington, D.C., receiving the Outstanding Handicapped Federal Employee of the Year Award in 1979. In 1984 he was made a special assistant in the Navy Center for Applied Research in Artificial Intelligence at NRL but left in 1984 to become Distinguished Professor of Computer Science at the University of Minnesota.
In these various positions Slagle helped mature the fledgling discipline of artificial intelligence, publishing the influential topic Artificial Intelligence in 1971. He developed an expert system designed to set up other expert systems—A Generalized Network-based Expert System Shell, or AGNESS. He also worked on parallel expert systems, artificial neural networks, time-based logic, and methods for uncovering causal knowledge in large databases. He died in 1994.
showed that computers could feasibly be used for programs that did not relate to business data processing. Fourth, the SAINT system showed how the use of heuristic rules and information could lead to the solution of problems that could not have been solved previously because of the amount of time needed to calculate a solution. SAINT’s major impact was in outlining the uses of these techniques, which led to continued research in the subfield of artificial intelligence that became known as expert systems.
See also BASIC programming language; CAD/CAM; COBOL computer language; Differential analyzer; FORTRAN programming language; Robot (industrial).

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