The surrounding space is constantly augmented by a myriad of devices that expose heterogeneous data, like slowerchanging data, dynamic data streams and functionalities. Developing applications that cope with heterogeneous data and diverse communication protocols is a tedious task. The success of such applications depends on the performance of data access and on the easy management of available data. To address these challenges, we propose UbiWare, a middleware that facilitates application development for ambient intelligence. We abstract the surrounding space as a databaselike environment and the heterogeneous entities and devices as data services that produce data. To query the distributed data services and access their data, we introduce an API that greatly simplifies application development and is compatible with the different operators used by query engines in Data Stream Management Systems or Pervasive Environment Management Systems.