Wireless sensor and actor networks (WSANs) con-such a dense deployment is usually not necessary for actor stitute a new pervasive technology and currently one of the nodes due to their higher capabilities. In some applications, most interesting fields of research. WSANs have two major integrated sensor/actor nodes, especially robots, may replace challenges: coordination mechanisms for both sensor-actor and actor-actor interactions, and real-time communication to perform actor nodes. correct and timely actions. This paper introduces a middleware A major challenge in WSNs that becomes even more architecture that address these two requirements and facilitate important in WSANs is the coordination requirement [10] [1]. the application programmer task. Our proposal supports a high-In WSANs two kinds of coordination, sensor-actor and actorlevel coordination model that is based on the use of tuple actor coordination, have to be taken into account. In particular, channels to achieve communication and synchronization among sensor-actor coordination provides the transmission of sensed the nodes. A tuple channel is a priority queue structure that sensor-actor to ators. te rcing sensed allows data structures to be communicated both in a one-to-data from sensors to actors. After receiving sensed data, actors many and many-to-one way, facilitating the data-centric behavior need to coordinate with each other in order to make decisions of sensor queries. The main characteristics of the model and the on the most appropriate way to perform the action. It has to different components forming the middleware are presented. In be decided whether the action requires exactly one actor (and addition, some implementation details and preliminary results of which one) or, on the contrary, it requires the combined effort the current prototype are described. o ne ors.of multiple actors.On the other hand, depending on the application there I. INTRODUCTION may be a need to respond rapidly to sensor input. Moreover, The combination of recent technological advances in elec-the collected and delivered sensor data must still be valid tronics, nanotechnology, wireless communications, computing, at the time of acting. Therefore, the real-time issue is a networking, and robotics has enabled the development of very important requirement in WSANs. Thus, coordination models and communication protocols should support real-time Wireless Sensor Networks (WSNs), a new form of distributed poete fti ido ytm computing where sensors (tiny, low-cost and low-power nodes, .tispe present a m fcia colloquially referred to as "motes") deployed in the environ-application development over WSANs. Our reference operamenut commuicatewienomessly2 toSgathaerand report informati tional setting is based on a scenario where there is a dense about phyical phenomena s hav envsuccessfl deployment of stationary sensors forming clusters, each one used for various application areas, suchas eironme governed by a (possibly mobile) actor. Communication bemonion objct and e tween a cluste...
