The different components of Ubiquitous Oulu, the large displays, sensors, users’ own devices and the networks they use form an extensive decentralized system. It is organized with the help of UBI middleware which hides the differences between components and offers open homogenous interfaces for the use of different resources of the system. This is how, in the future, the entire community can make good use of the arising infrastructure in their own research and development actions.

A central part of the middleware is the asynchronous communications based on the publish-subscribe model which enables the communication between reactive and proactive programs in decentralized environments. The publish-subscribe model is broadly used in realising dynamic systems. Typically in these systems, the components are not necessarily known in advance but the communications system routes the messages in decentralized environments according to the conditions set by the subscriber or the terms set in the application servers. Therefore, this model conforms well as a building block for the applications of ubiquitous information technology. An important part of the communications solution is the content-based routing of the messages which enables the accurate allocation of information for the subscribers. For example, a message can be directed into a certain logical or physical space, such as to all users in a market place who have been there for ten minutes. Content- and context-based actions enable new types of interactive applications.