Writing Graphical User Interfaces (GUI) is time and effort consuming, and when they have to evolve, doing changes could become quickly a nightmare. Hand-writing code for GUI is complex as the code is spread over several source files and their relationship is not always obvious. By using a visual designer, the programmer avoids writing boilerplate code, but semantic information remains stored at the source code level. A model-based approach help to raise the level of abstraction.
The benefit of modeled UIs could be reduced if changes in the models require each time an explicit regeneration step. In order to shorten this turnaround time, models will not lead to code generation but are interpreted at runtime. Dynamic or live models for UI make it possible to modify models faster at design time enable models changes at runtime and even to debug models while running the application.