Mobile applications are deployed in highly dynamic environments. Devices have limited resources available and the user context changes frequently. This introduces new requirements for applications, and requires that applications are able to adapt during runtime. In addition, developers must be able to incrementally add new behaviour to applications as required by unanticipated situations. Current approaches to mobile application development and architectures do not properly address these requirements of mobile applications. This work proposes a framework, based on coordination principles, which is able to facilitate the required methods of adaptation. The framework incorporates a methodology and an architecture. The architecture provides significant advantages over previous work in terms of adaptation support. The methodology provides developers with a development process and guidelines whereby adaptive applications may be specified. As new requirements of existing applications emerge, developers can build and deploy additions to applications during runtime. The research has been evaluated through the design of application prototypes. These were built through the use of an implemented toolkit for application development, which is based on the specified methodology. The architecture, methodology and toolkit provide a unifying framework for mobile applications. The work presented in this thesis closes a gap in existing knowledge in the design and execution of distributed mobile applications.