The OpenSense project addresses key research challenges in the domain of information and communication systems related to community-based sensing using wireless sensor network technology in the context of air pollution monitoring, such as : i) Reducing noise and data volume of heterogeneous sensor data by exploiting redundancies derived from complex environmental processes. Previous approaches only treated very regular sensor configurations and simple processes. ii) Performing real-time data gathering with heterogeneous and mobile sensors and intermittent connectivity, in particular in urban environments. iii) Compiling numerical models of complex spatial processes into qualitative approximations that can be used for efficient signal processing and sensor interpretation. iv) Sharing measurement and model data through an open community platform in a trusted and fair environment, providing security against manipulation and faulty data. OpenSense is a project within the Swiss nano-tera program.