Abstract. The explicit management of Quality of Service (QoS) of network connectivity, such as, e.g., working cost, transaction support, and security, is a key requirement for the development of the novel wide area network applications. In this paper, we introduce a foundational model for specification of QoS attributes at application level. The model handles QoS attributes as semantic constraints within a graphical calculus for mobility. In our approach QoS attributes are related to the programtractions and are exploited to select, configure and dynamically modify the underlying system oriented QoS mechanisms.