[This README: created in 1995.  Contact info updated 5/20/2002.
 Updated for ANSI CL 7/14/2004.]
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INTRODUCTION

Welcome to the Don Theorem Prover (DTP), version 3.00

DTP is an inference engine for first-order predicate calculus, and it
specializes in domain-independent control of reasoning.

Please send comments to Don Geddis at
	don@geddis.org
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IMPLEMENTATION

The original code was developed under Franz Allegro CL 4.2.beta.0 on a Sun
Sparc, written in Common Lisp of the CLtL2 era.  Earlier versions were tested
on MCL 2.0p2 (Apple Macintosh) and Lucid HP Common Lisp Rev. A.04.01 (HP-9000
Series 300/400).

In 2004 the core code was revised to conform to ANSI Common Lisp.  Some
optional extensions require non-ANSI functions; these are most likely to
work with the CMUCL implementation, as well as perhaps Franz Allegro.
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AVAILABILITY

DTP is available on the World Wide Web (WWW) from
	http://don.geddis.org/dtp/
in the file
	dtp.tar.gz	ANSI Common Lisp source code + logic puzzle examples
This file contains directories which have been run through the unix "tar"
program and then compressed with the GNU zip utility ("gzip").
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DOCUMENTATION

The postscript documentation is available in the same DTP directory:
	http://don.geddis.org/dtp/manual.ps.gz
Also of interest may be my thesis, available as
	http://don.geddis.org/dtp/thesis.ps.gz

Most of the functionality is shown in the examples in the logical theories,
which are exercised by running the function (TEST-DTP).  It is often useful
to run some of those examples by hand, in particular after turning on full
tracing output with a sequence like this:
	(SETQ *THEORY* '<some theory>)
	(SETQ *TRACE* (POSSIBLE-VALUES '*TRACE*))
	(PROVE '<some goal>)

Other new functions of interest include:
  (SETTINGS)            Describes the state of the theorem prover options
  (POSSIBLE-SETTINGS)   Describes the possible states of the options
  (SHOW <object>)       Takes a proof object or an answer object and generates
                        a postscript graph of the space
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VERSION

Version history:
	3.00	ANSI CL
	2.13	Contact info, code simplification
	2.12	Term simplification on answers (as well as literals)
	2.11	Fixed pure literal elim + proc attachment interaction
	2.10	Simplified "view" proof figures
	2.09	Re-introduced forking conjunctions
	2.08	Merged answers and reduction answers
	2.07	Iteration, on subgoal and function depth
	2.06	Simplified conjunction solving (removed forward inference)
	2.05	TPTP Library tools
	2.04	General "view" tool on proofs and answers
	2.03	Reduction check at conjunct instead of subgoal
	2.02	Depth limits and iteration (broken)
	2.01	Corrected reduction inference combined with caching
	2.00	Subgoaling inference system
	1.00	Resolution-based inference system
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RECOMMENDED SYSTEMS

There are two auxiliary systems that make DTP more useful.  For constructing
postscript graphs of the proof spaces, AT&T's "dot" program is required.
This is available as one of the modules in the open source project "graphviz":
     http://www.research.att.com/sw/tools/graphviz/
Of course, some mechanism for viewing the output is also needed: either a
postscript previewer like the unix utility "ghostview", or else a postscript
printer.

A large number of theorem proving examples can be found in the TPTP (Thousands
of Problems for Theorem Provers) collection:
     http://www.cs.miami.edu/~tptp/
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