Routing issue

I have presently this in my routes.rb

map.resources :media_containers , :has_many=> [:media_items]

as the media_items can have 'libraries' and 'medias' inheritances (STI)

rather than writing a route for a new media_item, with a parameter to specify the type (elibrary or not) , like :

new_media_container_media_item_path(@media_container, :lib => "1") .. or :lib=> "0" /media_container/media_container_id/media_items/new :action => new, :controller => media_items

I would like to have an URL like this (hidding the /media_items)

new_media_container_elibrary_path(@media_container) /media_container/media_container_id/new_library :action => new_library, :controller => media_items (!!) and new_media_container_emedia_path(@media_container) /media_container/media_container_id/new_media :action => new_media :controller => media_items (!!)

is this possible ? how should I define it in my routes.rb ?

thanks fyh

erwin