Combining tags in URLs

Hello,

I had seen an example on a blog entry about how to combine multiple
tags in the URL of a Web application that I think was written in Ruby
on Rails. In the example there were two kinds of URLs:

http://foo.bar.com/tag/nyc/losangeles/chicago would return a list of
items tagged ‘nyc’ AND ‘losangeles’ AND ‘chicago’

http://foo.bar.com/tag/nyc+losangeles+chicago would return a list of
items tagged ‘nyc’ OR ‘losangeles’ OR ‘chicago’

I would like to implement something similar for a Web application. Has
anyone seen this example or alternatively, can someone outline how I
could do this (with reference to what kinds of routes I’d put in
${APPROOT}/config/routes.rb).

Many thanks for your help in advance.

Vishy.