Analsysis by Propagation of Constraints in Elementary Geometry Problem Solving

Abstract

This paper describes GEL, a new geometry theorem prover. GEL is the result of an attempt to transfer the problem solving abilities of the EL electronic circuit analysis program of Sussman and Stallman to the domain of geometric diagrams. Like its ancestor, GEL is based on the concepts of "one-step local deductions" and "macro-elements." The performance of this program raises a number of questions about the efficacy of the approach to geometry theorem proving embodied in GEL, and also illustrates problems relating to algebraic simplification in geometric reasoning.