This invention provides a method and system for developing a software application program with user interfaces that make resource files external to the other compiled executable files such that the information from the resource file may be obtained at runtime as needed without the need for compilation. The external resource file may be edited at runtime to allow designers to modify the application's interface without having to depend on developers implement changes in the interface. This is achieved by providing resources in a markup language and routines that locate and parse the markup language text on the fly as an application executes. Compartmentalization of the effort in developing and porting an application is facilitated for protection of source code and better management of designers and developers working on different aspects of a software application due to the externalization of the resource files needed primarily by the designers.