DFG2DFG(1)							       SPASS								DFG2DFG(1)

NAME

       dfg2dfg - calculate approximations of problems

SYNOPSIS

       dfg2dfg [-horn] [-monadic] [-linear] [-shallow] [infile] [outfile]

DESCRIPTION

       dfg2dfg is a program that reads clauses from an input file in DFG syntax.  It then calculates an approximation of the clause set depending
       on the command line options.  Finally it writes the approximated clause set in DFG syntax to a file.

       If neither infile nor outfile are given, dfg2dfg reads from standard input and writes to standard output.  If one file name is given, it
       reads from that file and writes the output to standard output.  If more than one file name is given, dfg2dfg reads from the first file and
       writes to the second.

       The approximations are described in technical detail in the separate paper dfg2dfg.ps included in the SPASS distribution.

OPTIONS

       dfg2dfg has four different command line options that may be combined.

       -horn
	   This option enables the transformation of non-horn clauses into horn clauses.  Each non-horn clause with n positive literals is
	   transformed into n horn clauses, where the i-th clause contains the i-th positive literal and all negative literals of the non-horn
	   clause.  See also section 3 of the paper.

       -monadic[=n]
	   With this option atoms with non-monadic predicate symbols are transformed into monadic atoms.  If n is omitted or n=1 a term encoding
	   is applied, i.e., all non-monadic predicates are moved to the term level.  With n=2 a projection is applied. All non-monadic atoms are
	   replaced by their monadic argument projections.  See section 4.1 section 4.2 of the paper for more details.

       -linear
	   This approximation transforms a clause with monadic literals and non-linear variable occurrences in succedent atoms, into a new clause
	   with possibly more negative literals, that doesn't contain any non-linear variables in the succedent.  See section 5 of the paper for
	   details.

       -shallow[=n]
	   This transformation tries to reduce the depth of the terms in positive literals.  The transformation is applied to horn clauses with
	   monadic literals only.  If n is omitted or n=1 a strict transformation is applied, that is equivalence preserving, however.	For n=2
	   some preconditions are removed.  This allows the transformation to be applied more often, but the transformation isn't equivalence
	   preserving any more.  For n=3 even more preconditions are removed.  Take a look at section 6.n of the paper for the details of the
	   command line option -monadic=n.

SEE ALSO

       SPASS(1)

AUTHORS

       Enno Keen

       Contact : spass@mpi-inf.mpg.de

perl v5.10.0							    2010-02-23								DFG2DFG(1)