Nowadays, the users of Wireless Sensor and Actuator Networks (WSAN) are becoming more and more demanding in terms of choice and diversity of applications, and the identification of their characterization parameters is thus in order. This paper describes the WSAN characterisation parameters and is an update of a previous work, but new parameters were added and new characteristics were proposed. The gathering of all these parameters allowed us to sketch up taxonomy for WSAN via an application-oriented approach, identifying the services offered by each application. For comparison purposes, tables with details from different projects in the field of WSAN are presented.