Class: Rools::RuleSet

Inherits:
Base
  • Object
show all
Defined in:
lib/rools/rule_set.rb

Constant Summary collapse

PASS = 
:pass
FAIL = 
:fail
UNDETERMINED = 
:undetermined

Instance Attribute Summary collapse

Instance Method Summary collapse

Methods inherited from Base

#logger, logger=

Constructor Details

#initialize(file = nil, &b) ⇒ RuleSet

You can pass a set of Rools::Rules with a block parameter, or you can pass a file-path to evaluate.



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# File 'lib/rools/rule_set.rb', line 19

def initialize(file = nil, &b)
  
  @rules = {}
  @facts = {}
  @dependencies = {}
  
  if block_given?
    instance_eval(&b)
  elsif file
    # loading a file, check extension
    name,ext = file.split(".")
    logger.debug("loading ext: #{name}.#{ext}") if logger
    case ext
      when 'csv'
        load_csv( file )
        
      when 'xml'
        load_xml( file )
        
      when 'rb'
        load_rb( file )
          
      when 'rules'  # for backwards compatibility
        load_rb(file)
        
      else
        raise RuleLoadingError, "invalid file extension: #{ext}"
    end
   end
end

Instance Attribute Details

#facts(name, &b) ⇒ Object (readonly)

facts can be created in a similar manner to rules all names are converted to strings and downcased. Facts name is equivalent to a Class Name

Example

require 'rools'

rules = Rools::RuleSet.new do

  facts 'Countries' do
  	["China", "USSR", "France", "Great Britain", "USA"]
  end

  rule 'Is it on Security Council?' do
    parameter String
  	condition { countries.include?(string) }
  	consequence { puts "Yes, #{string} is in the country list"}
  end
end

rules.assert 'France'



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# File 'lib/rools/rule_set.rb', line 178

def facts
  @facts
end

#num_evaluated ⇒ Object (readonly)

Returns the value of attribute num_evaluated.



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# File 'lib/rools/rule_set.rb', line 11

def num_evaluated
  @num_evaluated
end

#num_executed ⇒ Object (readonly)

Returns the value of attribute num_executed.



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# File 'lib/rools/rule_set.rb', line 11

def num_executed
  @num_executed
end

#status ⇒ Object (readonly)

Returns the value of attribute status.



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# File 'lib/rools/rule_set.rb', line 11

def status
  @status
end

Instance Method Details

#add_relevant_rules_for_fact(fact) ⇒ Object

for a particular fact, we need to retrieve the relevant rules and add them to the relevant list



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# File 'lib/rools/rule_set.rb', line 272

def add_relevant_rules_for_fact fact
  @rules.values.select { |rule| 
    if !@relevant_rules.include?( rule)
        if rule.parameters_match?(fact.value) 
          @relevant_rules << rule 
          logger.debug "#{rule} is relevant" if logger
        else
          logger.debug "#{rule} is not relevant" if logger          
        end 
    end
  } 
end

#assert(*objs) ⇒ Object

Turn passed object into facts and evaluate all relevant rules Previous facts of same type are removed



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# File 'lib/rools/rule_set.rb', line 261

def assert( *objs )
  objs.each { |obj| 
    fact(obj)
  }
  return evaluate()
end

#delete_facts ⇒ Object

Delete all existing facts



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# File 'lib/rools/rule_set.rb', line 209

def delete_facts
    @facts = {}
end

#evaluate ⇒ Object

evaluate all relevant rules for specified facts



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# File 'lib/rools/rule_set.rb', line 305

def evaluate
  @status = PASS
  @assert = true
  @num_executed = 0;
  @num_evaluated = 0;
  
  get_relevant_rules()
  logger.debug("no relevant rules") if logger && @relevant_rules.size==0
  
  #begin #rescue
    
    # loop through the available_rules, evaluating each one,
    # until there are no more matching rules available
    begin # loop
      
      # the loop condition is reset to break by default after every iteration
      matches = false
      obj     = nil #deprecated
 
      #logger.debug("available rules: #{available_rules.size.to_s}") if logger
      @relevant_rules.each do |rule|
        # RuleCheckErrors are caught and swallowed and the rule that
        # raised the error is removed from the working-set.
        logger.debug("evaluating: #{rule}") if logger
        begin
          @num_evaluated += 1
          if rule.conditions_match?(obj)
            logger.debug("rule #{rule} matched") if logger
            matches = true
            
            # remove the rule from the working-set so it's not re-evaluated
            @relevant_rules.delete(rule)
            
            # find all parameter-matching dependencies of this rule and
            # add them to the working-set.
            if @dependencies.has_key?(rule.name)
              logger.debug( "found dependant rules to #{rule}") if logger
              @relevant_rules += @dependencies[rule.name].select do |dependency|
                dependency.parameters_match?(obj)
              end
            end
            
            # execute this rule
            logger.debug("executing rule #{rule}") if logger
            rule.call(obj)
            @num_executed += 1
            
            # break the current iteration and start back from the first rule defined.
            break
          end # if rule.conditions_match?(obj)
          
        rescue RuleConsequenceError
          fail
        rescue RuleCheckError => e
          fail
        end # begin/rescue
        
      end # available_rules.each
      
    end while(matches && @assert)
    
  #rescue RuleConsequenceError => rce
    # RuleConsequenceErrors are allowed to break out of the current assertion,
    # then the inner error is bubbled-up to the asserting code.
  #  @status = FAIL
  #  raise rce.inner_error
  #end
  
  @assert = false
  
  return @status
end

#extend(name, &b) ⇒ Object

Use in conjunction with Rools::RuleSet#with to create a Rools::Rule dependent on another. Dependencies are created through names (converted to strings and downcased), so lax naming can get you into trouble with creating dependencies or overwriting rules you didn’t mean to.



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# File 'lib/rools/rule_set.rb', line 217

def extend(name, &b)
  name.to_s.downcase!
  @extend_rule_name = name
  instance_eval(&b) if block_given?
  return self
end

#fact(obj) ⇒ Object

A single fact can be an single object of a particular class type or a collection of objects of a particular type



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# File 'lib/rools/rule_set.rb', line 187

def fact( obj )
  #begin
    # check if facts already exist for that class
    # if so, we need to add it to the existing list
    cls = obj.class.to_s.downcase
    cls.gsub!(/:/, '_')
    if @facts.key? cls
      logger.debug( "adding to facts: #{cls}") if logger
      @facts[cls].fact_value << obj
    else
      logger.debug( "creating facts: #{cls}") if logger
      arr = Array.new
      arr << obj
      proc = Proc.new { arr }
      @facts[cls] = Facts.new(self, cls, proc ) 
    end
  #rescue Exception=> e
  #  logger.error e if logger
  #end
end

#fail(message = nil) ⇒ Object

Stops the current assertion and change status to :fail



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# File 'lib/rools/rule_set.rb', line 242

def fail(message = nil)
  @status = FAIL
  @assert = false
end

#get_facts ⇒ Object

returns an array of facts



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# File 'lib/rools/rule_set.rb', line 131

def get_facts
  @facts
end

#get_relevant_rules ⇒ Object

get all relevant rules for all specified facts



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# File 'lib/rools/rule_set.rb', line 296

def get_relevant_rules
  @relevant_rules = Array.new
  @facts.each { |k,f| 
    add_relevant_rules_for_fact f
  }
  sort_relevant_rules
end

#get_rules ⇒ Object

returns all the rules defined for that set



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# File 'lib/rools/rule_set.rb', line 138

def get_rules
  @rules
end

#load_csv(file) ⇒ Object

Loads decision table



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# File 'lib/rools/rule_set.rb', line 53

def load_csv( file )
  csv = CsvTable.new( file )
  logger.debug "csv rules: #{csv.rules}" if logger
  instance_eval(csv.rules)
end

#load_rb(file) ⇒ Object

Ruby File format loading



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# File 'lib/rools/rule_set.rb', line 114

def load_rb( file )
  begin
    str = IO.read(file)
    load_rb_rules_as_string(str)
  rescue Exception => e
    raise RuleLoadingError, "loading ruby file"
  end
end

#load_rb_rules_as_string(str) ⇒ Object

load ruby rules as a string



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# File 'lib/rools/rule_set.rb', line 124

def load_rb_rules_as_string( str )
  instance_eval(str)    
end

#load_xml(fileName) ⇒ Object

XML File format loading



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# File 'lib/rools/rule_set.rb', line 62

def load_xml( fileName )
  begin
    str = IO.read(fileName)
    load_xml_rules_as_string(str)
  rescue Exception => e
    raise RuleLoadingError, "loading xml file"
  end
end

#load_xml_rules_as_string(str) ⇒ Object

load xml rules as a string



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# File 'lib/rools/rule_set.rb', line 72

def load_xml_rules_as_string( str )
  begin
    doc = REXML::Document.new str
    doc.elements.each( "rule-set") { |rs| 
      facts = rs.elements.each( "facts") { |f| 
        facts( f.attributes["name"] ) do f.text.strip end
      }
      
      rules = rs.elements.each( "rule") { |rule_node|
         rule_name  = rule_node.attributes["name"]
         priority   = rule_node.attributes["priority"]
         
         rule       = Rule.new(self, rule_name, priority, nil)
         
         parameters = rule_node.elements.each("parameter") { |param|
            #logger.debug "xml parameter: #{param.text.strip}"
            rule.parameters(eval(param.text.strip))
         } 
         
         conditions = rule_node.elements.each("condition") { |cond|
            #logger.debug "xml condition #{cond}"
            rule.condition do eval(cond.text.strip) end
         } 
   
         consequences = rule_node.elements.each("consequence") { |cons|
           #logger.debug "xml consequence #{cons}"
           rule.consequence do eval(cons.text.strip) end
         } 
         
         @rules[rule_name] = rule
      }
      logger.debug( "loaded #{rules.size} rules") if logger
    }
  rescue Exception => e
    raise RuleLoadingError, "loading xml file"
  end
  
end

#rule(name, priority = 0, &b) ⇒ Object

rule creates a Rools::Rule. Make sure to use a descriptive name or symbol. For the purposes of extending Rules, all names are converted to strings and downcased.

Example

rule 'ruby is the best' do
  condition { language.name.downcase == 'ruby' }
  consequence { "#{language.name} is the best!" }
end



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# File 'lib/rools/rule_set.rb', line 150

def rule(name, priority=0, &b)
  name.to_s.downcase!
  @rules[name] = Rule.new(self, name, priority, b)
end

#rule_assert(obj) ⇒ Object

an assert has been made within a rule



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# File 'lib/rools/rule_set.rb', line 250

def rule_assert( obj )
  # add object as a new fact
  f = fact(obj)
  # get_relevant_rules
  logger.debug( "Check if we need to add more rules") if logger
  add_relevant_rules_for_fact(f)
  sort_relevant_rules
end

#sort_relevant_rules ⇒ Object

relevant rules need to be sorted in priority order



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# File 'lib/rools/rule_set.rb', line 288

def sort_relevant_rules
  # sort array in rule priority order
  @relevant_rules = @relevant_rules.sort do  |r1, r2| 
    r2.priority <=> r1.priority 
  end
end

#stop(message = nil) ⇒ Object

Stops the current assertion. Does not indicate failure.



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# File 'lib/rools/rule_set.rb', line 237

def stop(message = nil)
  @assert = false
end

#with(name, prio = 0, &b) ⇒ Object

Used in conjunction with Rools::RuleSet#extend to create a dependent Rools::Rule

Example

extend('ruby is the best').with('ruby rules the world') do
  condition { language.age > 15 }
  consequence { "In the year 2008 Ruby conquered the known universe" }
end



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# File 'lib/rools/rule_set.rb', line 230

def with(name, prio=0, &b)
  name.to_s.downcase!
   (@dependencies[@extend_rule_name] ||= []) << Rule.new(self, name, prio, b)
   #@rules[name] = Rule.new(self, name, prio, b)
end