This paper presents SAGA, a functional software architecture for distributing sensor data. The recursive architecture is dynamically instantiated for collecting, composing and storing data at multiple locations. Objectives are to support devices that are intermittently connected over different access-technologies, to save energy by avoiding repetitive transmission from sensors, and to scale out data compositions for different application services. When the architecture is instantiated the entities form a directed graph across organizational boundaries between sensors and applications. Data may be retrieved from sensors on-demand or be disseminated in real-time, for composition and delivery to the applications. The architecture is based on current sensor network principles such as client-server, representational state transfer and web services. The architecture is presented together with identified key requirements and design choices, and it has been instantiated in a prototype implementation for a smart city application. Some key issues for further research are presented.