Routing Module to mixin

I have a need to get routes into my AR models, but I can not find the
module that provides them to ActionController. For example, I would
like to provide an event feed from two different locations, so want to
do something like this;

xml.instruct! :xml, :version => '1.0'
xml rss stuff
@events.each do |event|
  event.to_rss(xml)
end

Event.rb
def to_rss(xml)
  xml.item do
    xml.link(event_url(self))
    xml.guid(event_url(self))
  end
end

but AR (rightly) doesn't know how to do event_url() Where does it
come from?

Thanks,
--Dean