CMU Artificial Intelligence Repository
FOCL: Expert System Shell and Machine Learning Program
FOCL is an expert system shell and machine learning program written in
Common Lisp. The machine learning program extends Quinlan's FOIL
program by containing a compatible explanation-based learning
component. FOCL learns Horn Clause programs from examples and
(optionally) background knowledge. The expert system includes a
backward-chaining rule interpreter and a graphical interface to the
rule and fact base.
The Macintosh version includes a graphical interface that displays the
search space explored by FOCL, so it is a useful pedagogical tool.
This application also contains a graphical interface for building rule
bases, so you can ignore the machine learning aspects, and use it as
an expert system shell with the following capabilities:
+ A backward-chaining rule interpreter.
+ A graphical rule and fact editor.
+ Graphical display of the rule base.
+ (Simple) Natural language explanation of inferences
+ Menu-based facilities for editing rules and adding natural language
translations to rules.
+ Optional typing of variables and checking the rule base for type
+ Tracing of rules
+ Analysis of the accuracy of rules in a rule base.
Sample rule bases are included.
The Common Lisp source code is limited to portable source code for
the machine learning program only, since the interface depends on
as the files README.FOCL-1-2-3, FOCL-1-2-3-manual.hqx,
FOCL-1-2-3.tar.Z, and FOCL-1-2-3.cpt.hqx
Version: 2.1 (21-APR-94)
Requires: Common Lisp
Copying: If you use a copy of FOCL, please send mail to
so they can inform you of upgrades.
CD-ROM: Prime Time Freeware for AI, Issue 1-1
Author(s): Mike Pazzani
Irvine, CA 92717 USA
Contact: Michael Pazzani
Authors!Brunk, Authors!Pazzani, Backward Chaining, EBL,
Expert System Explanation, Expert System Shells, FOCL,
Horn Clauses, Lisp!Code, Machine Learning
Pazzani, M. and Kibler, D., "The role of prior knowledge in inductive
learning", Machine Learning 9:54-97, 1992.
Last Web update on Mon Feb 13 10:24:18 1995