dfg2dfg - calculate approximations of problems
dfg2dfg [-horn] [-monadic] [-linear] [-shallow] [infile] [outfile]
dfg2dfg is a C-program that reads clauses from an input file in DFG
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
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.
dfg2dfg has four different command line options that may be combined.
- 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.
- With this option atoms with non-monadic predicate symbols are transformed into
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.
- 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
See section 5 of the paper for details.
- This transformation tries to reduce the depth of the terms in positive
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.
Contact : Thomas Hillenbrand <email@example.com>
Christoph Weidenbach <firstname.lastname@example.org>
11.6 SEE ALSO
This document was generated
by Renate Schmidt on March, 10 2003