RESTRack is a Rack-based MVC framework that makes it extremely easy to develop RESTful data services. It is inspired by Rails, and follows a few of its conventions. But it has no routes file, routing relationships are done through supplying custom code blocks to class methods such as "has_relationship_to" or "has_mapped_relationships_to". RESTRack aims at being lightweight and easy to use. It will automatically render JSON and XML for the data structures you return in your actions (any structure parsable by the "json" and "xml-simple" gems, respectively). If you supply a view for a controller action, you do that using a builder file. Builder files are stored in the view directory grouped by controller name subdirectories (`view/<controller>/<action>.xml.builder`). XML format requests will then render the view template with the builder gem, rather than generating XML with XmlSimple.