# File lib/dm-serializer/to_xml.rb, line 23
    def to_xml_document(opts={}, doc = nil)
      xml = XML.serializer
      doc ||= xml.new_document

      default_xml_element_name = lambda {
        DataMapper::Inflector.underscore(model.name).tr("/", "-")
      }

      root = xml.root_node(
        doc,
        (opts[:element_name] || default_xml_element_name[])
      )

      properties_to_serialize(opts).each do |property|
        value = __send__(property.name)
        attrs = {}

        unless property.primitive == String
          attrs['type'] = property.primitive.to_s.downcase
        end

        xml.add_node(root, property.name.to_s, value, attrs)
      end

      Array(opts[:methods]).each do |meth|
        if self.respond_to?(meth)
          xml_name = meth.to_s.gsub(/[^a-z0-9_]/, '')
          value = __send__(meth)

          unless value.nil?
            if value.respond_to?(:to_xml_document)
              xml.add_xml(root, value.to_xml_document)
            else
              xml.add_node(root, xml_name, value.to_s)
            end
          end
        end
      end

      doc
    end