SEO friendly routing

Hi all!

I'm moving to Ruby on Rails from PHP/ZendFramework. And i cannot understand how to make such routing model:

I am trying to develop articles site from scratch, so i have article model with fields: id, title, section, alias and body, also i have sections tree for navigation, each section has fields: id, parent_id, title, alias.

I want to have each article have path like {root_section_alias}/{subsection_alias}/{article_alias}

Example urls:

http://localhost/news/spb/ramstain-rullezz http://localhost/humor/some-humor-article

Try the plugin at http://github.com/smsohan/acts_as_permalinkable