An application generation environment coordinates development of component-based two-tiered applications using a unifying data model comprising an interconnected model of objects. The data model unifies the two-tiered application to present a single logical application for visualisation and for programming using a graphical user interface. The data model transparently programs tiers of the application in response to user input to program the single logical application. Application components are generated for execution within a two-tiered execution environment such as a client device (e.g. a wireless mobile device) and a gateway server providing a stateful proxy with which to access services or a remote data source via a network. The application components may by generated with marks to denote portions thereof for execution within the respective tiers of the two-tiered execution environment.