Another goal is to use information in it’s native form where ever possible. Models and forms in many frameworks are built by hand (with the exception of the venerable Rails and the youthful Cake) and often duplicate the information that’s already available (and programmatically accessible) in a schema: SQL, Relax NG, XML Schema Definition, etc. The goal is to use these as building blocks for generic objects that can then be extended by the developer. In theory it’s very similar to Rails ActiveRecord, but for more than databases.