Model-driven engineering (MDE) techniques address rapid changes anguages and platforms by lifting the abstraction level from code to models. On the one hand models are transformed for model elaboration and translation to code; on the other hand models can be executable. We demonstrate how both approaches are used in a complementary way in UML-based Web Engineering (UWE). Rule-based transformations written in ATL are defined for all model-to-model transitions, and model-to-code transformations pertaining to content, navigation and presentation. An UWE run-time environment allows for direct execution of UML activity models of business processes.