lderes(1)

NAME
lderes - compute extensions of simple default theories

SYNOPSIS
lderes [options] file

DESCRIPTION
The program lderes computes extensions of simple default theories. There is a natural and rather simple embedding of logic programs into simple default theories; in the case of a logic program, lderes computes stable models of the program. Input is in DeReS format, and consists of three files: a .dt file which points to the other two files; a .dc file which contains the defaults, or rules, of the theory; and a .thc file, containing the initial set of facts (literals or conjunctions of literals). File formats are described below.

OPTIONS

-1, --single
    Compute a single extension. This is the default.

-a, --all
    Compute all extensions.

-c N, --count=N
    Compute the first N extensions.

-t, --time
    Perform timing. The CPU time in seconds used by parsing and computation, as well as the CPU time used in finding each extension (as measured by clock(3)) is displayed to stdout after the computation. This is the default.

-n, --no-time
    Do not display timing information.

-V, --verbose
    Display extra information to stderr and stdout. This flag causes lderes to display candidate numbers of extensions to stdout, and a number of status messages to stderr.

-m, --messages
    Display only error messages to stderr. Display extensions (and possibly timing information, depending on the state of the -t and -n flags) to stdout.

-q, --quiet
    Display nothing to stderr; display extensions and possibly timing information to stdout.

-qq, --very-quiet
    Display nothing to stderr. Also do not display extensions to stdout; count them only. Timing information may still be printed, depending on the state of the -t and -n flags.

-v, --version
    Print version information to stdout. The information indicates the version numbers of lderes and lpsms.

-h, --help
    Display usage information to stdout.

EXAMPLE USAGE
lderes -t -q -c 3 prog1 Compute the first three extensions of the program in prog1.dt, prog1.thc, prog1.dc, and prog1.str. lderes will display the extensions and timing information, but no other status messages, to stdout. lderes -V -1 prog2 Compute the first extension of the program found in prog2.dt, prog2.thc, prog2.dc, and prog2.str. Display that extension with its candidate number and timing information to stdout, and other status information to stderr.

FILE FORMATS
When given a filename file on the command line, lderes first opens file.dt. This file should contain two lines (in addition to any comments):
    w = wfile
    d = dfile
The default theory is then read from wfile.thc and dfile.dc. The first file contains expressions which are either literals or conjunctions of literals. Expressions are separated by blank lines. If smdtconv was used to produce the files, the .thc file will contain no expressions. The second file contains a set of defaults of the form:
    a : b1, b2, b3
         -> g;
The prerequisite, a, is a literal, a conjunction of literals, or a disjunction of literals. Conjunction is represented by “&&”, disjunction by “||”, and negation by “!”. The justifications b1 . . . b3, are also literals, conjunctions of literals, or disjunctions of literals. Finally, the conclusion, g, is a literal or conjunction of literals. Each default is separated from the next by a blank line. For the semantics of default logic, see [CMT]. In all three files, comments begin with % and extend to the end of a line.

AUTHOR
DeReS, a system for full default logic, was originally developed by Pawel Cholewinski. Matt Levy <mattlevy@csr.uky.edu> reimplemented DeReS as lderes, making great speed improvements in the process. lderes was made to conform to the command-line style of sderes and the rest of lpsms by Neil Moore <neil@cs.uky.edu>. Some fatal bugs were fixed by Artur Mikitiuk <artur@cs.uky.edu>. DeReS and lderes are Copyright © 1992-1999 The University of Kentucky. See the file COPYRIGHT in the lpsms distribution for details.

BUGS
Maybe.

SEE ALSO
sm2dt(1), smdtconv(1), stable(1), sderes(1), smodels(1).
[CMT] Pawel Cholewinski, Victor Marek, and Miroslaw Truszczynski, “Default Reasoning System DeReS”. Proceedings of KR, 1996. pp 518–528.