RABL (Ruby API Builder Language) is a Rails and Padrino ruby templating system for generating JSON, XML, MessagePack, PList and BSON. When using the ActiveRecord 'to_json' method, I find myself wanting a more expressive and powerful solution for generating APIs. This is especially true when the JSON representation is complex or doesn't match the exact schema defined within the database. Anyone who has tried the 'to_json' method used in ActiveRecord for generating a JSON response has felt the pain of this restrictive approach. RABL is a general templating system created to solve these problems by approaching API response generation in an entirely new way.