In this interview filmed at RubyFringe, Yehuda Katz talks about web framework Merb.
Merb follows a few design principles that distinguish it from Ruby on Rails. As Yehuda explains, Merb aims to provide a stable public API which can be used, and which is warded off from the actual Merb implementation. With that, 3rd party plugin providers don't have to worry about some change in the Merb implementation breaking their code. Hand in hand with this is a strict documentation for Merb code. Merb uses documentation conventions to describe the contract of a method, ie. the expected argument types and return types. As Yehuda mentions, the conventions resembled the one of the Ruby documentation tool Yard.
Other topics are the perils of Rails' Module#alias_method_chain (and why Merb won't use it) and how the Merb team handles Monkey Patching (Open Classes).
Watch "Yehuda Katz Explains Merb".