restful_authentication with web services


i have a question about using rails 1.2 for restful web services.
with the new features, it's really easy to get the results in xml.
however, i am struggling to have a login system to authenticate the
user. i am trying to utilize restful_authentication for the task.
but i am unable to find documentation on how to use the plugin with
xml. furthermore, once the user is authenticated, i was thinking
about keeping the person logged in by passing a token. however, i
don't know how to do that with restful_authentication as well. is
there another plugin i should look at? any help/directions would be
much appreciated.