NAME
    VS::RuleEngine::Loader::XML - Load VS::RuleEngine engine declarations in
    XML

SYNOPSIS
      use VS::RuleEngine::Loader::XML;
      
  my $engine = VS::RuleEngine::Loader::XML->load_file("my_engine.xml");
      $engine->run();
      
  my $other_engine = VS::RuleEngine::Loader::XML->load_string($xml);
      $other_engine->run();

DESCRIPTION
    This module provides a mean to load VS::RuleEngine engine declarations
    from XML.

INTERFACE
  CLASS METHODS
    load_file ( PATH )
        Loads the engine declaration from *PATH*.

    load_string ( XML )
        Loads the engine declaration from *XML*.

XML Document structure
    The document root element must be <engine>. Valid children are:

    *   <action> - Declares an action.

    *   <defaults> - Defines a default argument set

    *   <input> - Declares an input.

    *   <output> - Declares an output.

    *   <rule> - Declares a rule.

    *   <ruleset> - Groups a set of rules under a common name.

    *   <run> - Connects a set of rules to an action.

  Action, Input, Output and Rule elements
    The elements <action>, <input>, <output> and <rule> all have the
    following mandatory attributes:

    name
        The name of the entity to define in the engine.

    instanceOf
        The class that implements the entity and that'll be instansiated
        when the engine is runned.

    defaults
        The default arguments to the entity as defined by a previously
        declared <defaults>. Separate multiple defaults with comma and/or
        whitespace.

    If the class defined by *instanceOf* implements the method
    "process_xml_loader_args" it will be called as a class method with the
    "XML::LibXML::Element"-element as only argument. This method must return
    a list of arguments that will be passed to the constructor for the class
    when the entity is instansiated.

    If no "process_xml_loader_args" method is available the loader will
    interpret all children as a hash where the elements name is the key and
    its text content its value. If a child is an empty element, that is has
    no children (as in "<foo/>") its value will be undef. This hash will be
    passed to the constructor as a hash reference.

  Defaults
    By using the tag <defaults> t is possible to declare common arguments
    that can be reused by multiple entities. Its children will be
    interpreted as key/value pairs. The required attribute 'name' defines
    the name for the defaults.

  Rulesets
    By using the tag <ruleset> it is possible to give a set of rules a
    shared name that can later be used when binding together rules and
    actions.

    The attribute *name* is always expected and is used to give the ruleset
    its name which can be referenced later on by other rulesets or
    rule<->action mappings.

    To specify what rules to include it expects <rule>name of rule</rule
    and/or <ruleset>name of ruleset</ruleset> elements as children. Any
    other element will result in an error.

    In addition to specifying specific rules or contens of other rulesets it
    is also possible to include the rules that matches the criteria
    specified by the attributes:

    rulesMatchingName
        Include all rules that matches the name by the given Perl5 regular
        expression.

    rulesOfClass
        Include all rules which inherits from the given class.

    Note, if both attributes above are present it does not create a ruleset
    with the rule that matches both (i.e a union).

  Connecting rules and actions
    To connect an action to a rule use the <run> element. It expects the
    attribute *action* which must be the name of an already defined action.
    Which rules to invoke the action on is specified with children of type
    <rule>name of rule</rule and/or <ruleset>name of ruleset</ruleset>. Any
    other element will result in an error.

SEE ALSO
    VS::RuleEngine

BUGS AND LIMITATIONS
    Please report any bugs or feature requests to
    "bug-vs-ruleengine-loader-xml@rt.cpan.org", or through the web interface
    at <http://rt.cpan.org>.

AUTHOR
    Claes Jakobsson "<claesjac@cpan.org>"

LICENCE AND COPYRIGHT
    Copyright (c) 2007 - 2008, Versed Solutions "<info@versed.se>". 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.