RABL (Ruby API Builder Language) is a Rails and Padrino ruby templating system
for generating JSON, XML, MessagePack, PList and BSON. It provides a more
expressive and powerful solution for generating APIs than ActiveRecord's
'to_json' method.  It is particularly helpful when the JSON representation is
complex or doesn't match the exact schema defined within the database.

With it, one can easily:

 - Create arbitrary nodes with names based on combining data in an object
 - Pass arguments to methods and store the result as a child node
 - Render partial templates and inherit to reduce code duplication
 - Rename or alias attributes to change the name from the model
 - Append attributes from a child into a parent node
 - Include nodes only if a certain condition has been met

WWW: https://github.com/nesquena/rabl