CMU Artificial Intelligence Repository
NATHAN (Spec13): Argues defeasibly in first-order logic.
Nathan (specs1-13) is a relatively fast implementation of a defeasible
reasoner with specificity. It uses arguments of the kind described in
[1,2] and its specificity comparator (LMNOP) is described in  which
is a modification of the criterion of Poole.
It solves all basic benchmark problems to the author's satisfaction.
Its limitations in planning applications are due to the limits of its
underlying resolution-refutation linear-input set-of-support
theorem-prover for FOL.
It includes a predicate for unique names. It includes a perl
preprocessor for extracting rules from cases.
Email from R. Loui.
Copying: Copyright (c) 1994 by R. Loui.
Use, copying, and distribution permitted, provided that
NATHAN (and derivatives) are not included in a
CD-ROM: Prime Time Freeware for AI, Issue 1-1
Mailing List: None
Author(s): R. Loui, A. Costello, A. Merrill
Contact: Dr. R. P. Loui
Dept. of Computer Science
St. Louis, MO 63130
Argument, Authors!Costello, Authors!Loui, Authors!Merrill,
C!Code, Defeasible Reasoning, Dialectic, Inheritance, NATHAN,
Nonmonotonic Reasoning, Planning,
Reasoning!Nonmonotonic Reasoning, Specificity
A user's manual and typescript may be found at the top of the
Other relevant references include:
 Loui, R. P., "A system of defeasible inference", COMPUTATIONAL
INTELLIGENCE 3, 1987.
 Simari, G.R., and Loui, R.P., "Mathematics of defeasible
reasoning", ARTIFICIAL INTELLIGENCE 53, 1992.
 R.P. Loui, J. Norman, Andrew Merrill, J. Olson, Q. Stiefvater, and
Adam M. Costello, "Computing specificity", Washington University
CS Technical Report 93-03, 1993.
Last Web update on Mon Feb 13 10:27:48 1995