Quality of Service (QoS) plays a key role in service composition as services providing the same functionalities can be differentiated according to their QoS guarantees. We propose the ccpi calculus as a constraint-based model of QoS negotiations.

 

The cc-pi calculus combines basic operations of concurrent constraint programming with a symmetric, synchronous mechanism of interaction between senders and receivers. Furthermore, the cc-pi calculus is
parametric with respect to the choice of an underlying constraint system that is defined using a suitable semiring structure, equipped with a notion of names.

 

We adopt two case studies of SENSORIA: The telecommunication case study for specifying and enforcing Telco policies, the finance case study for showing how to model.