Database driven routes in CodeIgniter with caching

[eluser]Unknown[/eluser]
Hi, I was considering using something of this kind (which I consider neat and fast!) for a project I'm working on, but it seems to me this is only one side of the problem. I mean, here we are translating world-facing SEO-friendly URLs to internal routes that CI (and developers) can handle and work with. But on the other hand, how should we do invert this translation, to find out what URL we should use for what the developer sees as "/some_controller/some_method"? I don't think we can flip array keys and values to the routes array and apply CI routing code as is, because there may be many-to-one relationships that can't be inverted, in other words, for one "internal" route as "/some_controller/some_method" there should be only one official world-facing URL...