_validate

# File lib/rss/rss.rb, line 1118
    def _validate(ignore_unknown_element, tags, uri, models=self.class.models)
      count = 1
      do_redo = false
      not_shift = false
      tag = nil
      models = models.find_all {|model| model[1] == uri}
      element_names = models.collect {|model| model[0]}
      if tags
        tags_size = tags.size
        tags = tags.sort_by {|x| element_names.index(x) || tags_size}
      end

      models.each_with_index do |model, i|
        name, _, occurs, = model

        if DEBUG
          p "before"
          p tags
          p model
        end

        if not_shift
          not_shift = false
        elsif tags
          tag = tags.shift
        end

        if DEBUG
          p "mid"
          p count
        end

        case occurs
        when '?'
          if count > 2
            raise TooMuchTagError.new(name, tag_name)
          else
            if name == tag
              do_redo = true
            else
              not_shift = true
            end
          end
        when '*'
          if name == tag
            do_redo = true
          else
            not_shift = true
          end
        when '+'
          if name == tag
            do_redo = true
          else
            if count > 1
              not_shift = true
            else
              raise MissingTagError.new(name, tag_name)
            end
          end
        else
          if name == tag
            if models[i+1] and models[i+1][0] != name and
                tags and tags.first == name
              raise TooMuchTagError.new(name, tag_name)
            end
          else
            raise MissingTagError.new(name, tag_name)
          end
        end

        if DEBUG
          p "after"
          p not_shift
          p do_redo
          p tag
        end

        if do_redo
          do_redo = false
          count += 1
          redo
        else
          count = 1
        end

      end

      if !ignore_unknown_element and !tags.nil? and !tags.empty?
        raise NotExpectedTagError.new(tags.first, uri, tag_name)
      end

    end