NAME VS::RuleEngine - Generic rule based processing engine

SYNOPSIS A simple example which just randomizes a number 10 times and outputs it to screen if it was under 500.

  use VS::RuleEngine::Constants;
  use VS::RuleEngine::Declare;

  my $i = 0;

  my $engine = engine {
      prehook "check_i" => does {
          $i++;

          return KV_ABORT if $i == 10;
          return KV_CONTINUE;
      };

      input "random" => does {
          return int(rand(1000));
      };

      rule "under_500" => does {
          my $input = $_[KV_INPUT];
          return KV_MATCH if $input->get("random") < 500;
          return KV_NO_MATCH;
      };

      action "mark_under_500" => does {
          my ($input, $local) = @_[KV_INPUT, KV_LOCAL];
          $local->set("output" => $input->get("random") . " was under 500");
      };

      run "mark_under_500" => when "under_500";

      output "print" => does {
          my $local = $_[KV_LOCAL];
          my $output = $local->get("output");
          print $output, "\n" if defined $output;
      };
  }

A fictional spam filter

  use VS::RuleEngine::Constants;
  use VS::RuleEngine::Declare;

  my $engine = engine {
      prehook "has_more_email" => instanceof "MyApp::HasMoreEmails";

      # Returns an Email::Simple instance
      input "email" => instanceof "MyApp::GetEmail";

      input "from" => does {
            my $input = $_[KV_INPUT];
            return $input->get("email")->header("From");
      };

      rule "is_spam" => instanceof "MyApp::SpamDetector";

      rule "is_from_boss" => does {
          my $input = $_[KV_INPUT];

          if ($input->get("from") =~ /theboss@company\.com/) {
              return KV_MATCH;
          }

          return KV_NO_MATCH;
      };

      action "mark_for_deletion" => does {
          my $local = $_[KV_LOCAL];
          $local->set("delete-email" => 1);
      };

      run "mark_for_deletion" => when qw(is_spam is_from_boss);

      post_hook "process_mail" => does {
          my ($input, $local) = @_[KV_INPUT, KV_LOCAL];

          if ($local->get("delete-mail") == 1) {
              MyApp::EmailHandler->delete($input->get("email"));
          }

          return KV_CONTINUE;
      };
  };

  $engine->run();

DESCRIPTION VS::RuleEngine is a generic rule based processing engine. Processing is done while neither any pre nor post iteration hook aborts processing. Each engine supports multiple pre- and posthooks, inputs, output, actions and rules. An action is attached to one or several rules and is executed if any of the rules matches. Input is processed when needed and only once per iteration.

Multiple engines can be run in parallel in a runloop. Runloops can be
ran until no more data is available for processing or by a single step
at a time. This way multiple runloops may be executed simultaneously.

USAGE VS::RuleEngine has a declarative interface via VS::RuleEngine::Declare which is the simplest way to define engines. The synopsis shows an exmaple that could be implemented (with reservations for syntax errors).

Declarative interface VS::RuleEngine::Declare

Loading engines from other sources Currently creation of engines are only possible using either the declarative interface or by creating "VS::RuleEngine::Engine"-objects directly. Future releases will allow loading of engine declarations via XML and other formats.

Runloops Runloops transforms engines into something executable and runs them.

VS::RuleEngine::Runloop

Inputs, Outputs, Rules, Hooks, Actions The components that makes up an engine.

VS::RuleEngine::Input, VS::RuleEngine::Output, VS::RuleEngine::Rule, VS::RuleEngine::Hook,
VS::RuleEngine::Action

BUGS AND LIMITATIONS Please report any bugs or feature requests to "[email protected]", or through the web interface at http://rt.cpan.org.

AUTHOR Claes Jakobsson "[email protected]"

LICENCE AND COPYRIGHT Copyright (c) 2007, Versed Solutions "[email protected]". All rights reserved.

This software is released under the MIT license cited below.

The "MIT" License Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included
in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.