view release on metacpan or  search on metacpan

lib/AI/Logic/AnswerSet.pm  view on Meta::CPAN

DLV options like "-nofacts".
The output will be stored inside an array.

	my @out = AI::Logic::AnswerSet::singleExec("3col.txt","nodes.txt","edges.txt","-nofacts");

Another way to use this method:

	my @out = AI::Logic::AnswerSet::singleExec();

In this way it will work like C<executeAndSave()> without saving the output to a file.

=head3 iterativeExec

This method allows to call multiples DLV executions for several instances of the same problem.
Suppose you have a program that calculates the 3-colorability of a graph; in this case
one might have more than a graph, and each graph instance can be stored in a different file.
A Perl programmer might want to work with the results of all the graphs she has in her files,
so this function will be useful for this purpose.
Use it like in the following:

	my @outputs = AI::Logic::AnswerSet::iterativeExec("3col.txt","nodes.txt","./instances");

In this case the nodes of each graph are the same, but not the edges.
Notice that in order to correctly use this method, the user must specify the path 
to the instances (the edges, in this case).

The output of this function is a two-dimensional array; each element corresponds to the result
of a single DLV execution, exactly as in the case of the function C<singleExec()>.

=head3 selectOutput

This method allows to get one of the results of C<iterativeExec>.

	my @outputs = AI::Logic::AnswerSet::iterativeExec("3col.txt","nodes.txt","./instances");
	my @out = AI::Logic::AnswerSet::selectOutput(\@outputs,0);

In this case the first output is selected.

=head3 getASFromFile

Parses the output of a DLV execution saved in a file and gather the answer sets.

	AI::Logic::AnswerSet::executeFromFileAndSave("outprog.txt","dlvprog.txt","");
	my @result = AI::Logic::AnswerSet::getASFromFile("outprog.txt");

=head3 getAS

Parses the output of a DLV execution and gather the answer sets.

	my @out = AI::Logic::AnswerSet::singleExec("3col.txt","nodes.txt","edges.txt","-nofacts");
	my @result = AI::Logic::AnswerSet::getAS(@out);

=head3 mapAS

Parses the new output in order to save and organize the results into a hashmap.

	my @out = AI::Logic::AnswerSet::singleExec("3col.txt","nodes.txt","edges.txt","-nofacts");
	my @result = AI::Logic::AnswerSet::getAS(@out);
	my @mappedAS = AI::Logic::AnswerSet::mapAS(@result);

The user can set some constraints on the data to be saved in the hashmap, such as predicates, or answer sets, or both.

	my @mappedAS = AI::Logic::AnswerSet::mapAS(@result,@predicates,@answerSets);

For instance, think about the 3-colorability problem: imagine to 
have the edges in the hashmap, and to print the edges contained in the third answer set
returned by DLV; this is an example of the print instruction, useful to understand how
the hashmap works:

	print "Edges: @{$mappedAS[2]{edge}}\n";

In this case, we are printing the array containing the predicate "edge".

=head3 getPred

Easily manage the hashmap and get the desired predicate(see the print example
described in the method above):

	my @edges = AI::Logic::AnswerSet::getPred(\@mappedAS,3,"edge");

=head3 getProjection

Returns the projection of the n-th term of a specified predicate.
Suppose that we have the predicate "person" C<person(Name,Surename);> and
that we just want the surenames of all the instances of "person":

	my @surenames = AI::Logic::AnswerSet::getProjection(\@mappedAS,3,"person",2);

The parameters are, respectively: hashmap, number of the answer set, name of the predicate,
position of the term.

=head3 statistics

This method returns an array of hashes with some stats of every predicate of every answer set,
namely the number of occurrences of the specified predicates of each answer set.
If a condition is specified(number of predicates), only the answer sets that satisfy
the condition are returned.

	my @res = AI::Logic::AnswerSet::getAS(@output);
	my @predicates = ("node","edge");
	my @stats = AI::Logic::AnswerSet::statistics(\@res,\@predicates);

In this case the data structure returned is the same as the one returned by C<mapAS()>.
Hence, for each answer set (each element of the array of hashes), the hashmap will appear 
like this:

	{
		node => 6
		edge => 9
	}

This means that for a particular answer set we have 6 nodes and 9 edges.
In addition, this method can be used with some constraints:

	my @res = AI::Logic::AnswerSet::getAS(@output);
	my @predicates = ("node,"edge");
	my @numbers = (4,15);
	my @operators = (">","<");
	my @stats = AI::Logic::AnswerSet::statistics(\@res,\@predicates,\@numbers,\@operators);

Now the functions returns the answer sets that satisfy the condition, i.e., an answer set
is returned only if the number of occurrences of the predicate "node" is higher than 4, and the number of occurrences of the predicate "edge" less than 15.

=head3 getFacts

Get the logic program facts from a file or a string.

	my @facts = AI::Logic::AnswerSet::getFacts($inputFile);

or

	my $code = "a(X):-b(X). b(1). b(2).";
	my @facts = AI::Logic::AnswerSet::getFacts($code);

DLV code can be freely exploited, with the only constraint of putting a space between rules
or facts.
This is an example of wrong input code:

	my $code = "a(X):-b(X).b(1).b(2).";

=head3 addCode

Use this method to quiclky add new code to a string or a file.

	my $code = "a(X):-b(X). b(1). b(2).";
	AI::Logic::AnswerSet::addCode($code,"b(3). b(4).");

or

	my $file = "myfile.txt";
	AI::Logic::AnswerSet::addCode($file,"b(3). b(4).");

=head3 createNewFile

Creates a new file with some code.

	AI::Logic::AnswerSet::createNewFile($file,"b(3). b(4).");

=head3 addFacts

Quiclky adds facts to a file. Imagine to have some data(representing facts) 
stored inside an array; just use this method to put them in a file and give it a name.

	AI::Logic::AnswerSet::addFacts("villagers",\@villagers,">","villagersFile.txt");

In the example above, "villagers" will be the name of the facts; C<@villagers> is the array 
containing the data; ">" is the file operator(will create a new file, in this case); 
"villagersFile.txt" is the filename. The file will contain facts of the form "villagers(X)",
for each "X", appearing in the array C<@villagers>.


=head1 SEE ALSO

www.dlvsystem.com

=head1 AUTHOR

Ferdinando Primerano, E<lt>levia@cpan.orgE<gt>
Francesco Calimeri, E<lt>calimeri@mat.unical.itE<gt>

This work started within the bachelor degree thesis program of the
Computer Science course at Department of Mathematics of the University
of Calabria.

=head1 COPYRIGHT AND LICENSE

Copyright (C) 2012 by Ferdinando Primerano , Francesco Calimeri

This library is free software; you can redistribute it and/or modify
it under the same terms as Perl itself, either Perl version 5.10.1 or,
at your option, any later version of Perl 5 you may have available.


=cut