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
