I have developed a gem called ‘inferred slugs’. It’s compatible (as far as I know) with the rest of slug engines. The idea is that you don’t always need permalinks, and in this case, slugs are inferred from the information contained on the record itself, so no extra column is needed for the slug on your tables.
I have extensively written about the gem on my blog: http://blog.ereslibre.es/?p=343
The source code can be found here: https://github.com/ereslibre/inferred_slug
Any idea is welcome, and I’d be glad to know your opinions.
Rafael Fernández López.