class ActiveFedora::Base

def to_xml(xml=REXML::Document.new("<xml><fields/><content/></xml>"))
  fields_xml = xml.root.elements['fields']
  {:id => pid, :system_create_date => self.create_date, :system_modified_date => self.modified_date, :active_fedora_model => self.class.inspect}.each_pair do |attribute_name, value|
    el = REXML::Element.new(attribute_name.to_s)
    el.text = value
    fields_xml << el
  end
  datastreams.each_value do |ds|        
    ds.to_xml(fields_xml) if ds.kind_of?(ActiveFedora::MetadataDatastream) || ds.kind_of?(ActiveFedora::RelsExtDatastream)
  end
  return xml.to_s
end