Epilog Inference Package
According to the web site, the Epilog Inference Package 'is a library of Lisp subroutines that implement an efficient inference procedure for information encoded in SIF (Simplified Interchange Format). The inference procedure used in Epilog is based on a technique called model elimination.'
Epilog is free for educational and non-profit organizations (i.e. technically non-free)
Theorem Provers
This page is linked from: Epilog System and Episodic Logic
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