We are in the presence of a new and powerful technology called Wireless Sensor and Actor Networks. There are many fields where we can apply this technology to develop varied and interesting applications: high security environments, environmental monitoring,industrial monitoring, medicine, precision agriculture. This technology brings the need to develop new frameworks in order to make easier the application developer's task. Recently, different high-level programming abstractions and middleware have appeared as promising solutions. In this paper, a new service-oriented framework is introduced. The general scheme of the framework and a detailed description of the programming model are presented. The approach is oriented to deploy lightweight services on sensors and actors.Services can be composed among them by means of the port concept to form complex ad-hoc systems. A building monitoring and control application is described as a motivation example and it is used along the paper in order to show the expressiveness and usability of the abstract programming language proposed.