1. A method, comprising: presenting an application behavior specification and a presentation specification during run-time; receiving at least one input corresponding to a proposed modification to at least one of the application behavior specification and the presentation specification; determining permitted modifications to the at least one of the application behavior specification and the presentation specification based on a set of pre-defined rules; and generating a new application by modifying the at least one of the application behavior specification and the presentation specification at run-time based on the permitted modifications.