TY  - JOUR
SN  - 1567-8326
N2  - Service composition in Service Oriented Computing concerns not only integration of heterogeneous distributed applications but also dynamic selection of services. 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. At subscription time, a service requester and a provider may sign a contract recording the QoS of the supplied service. The cc-pi calculus has been introduced as a constraint-based model of QoS contracts. In this work we propose a variant of the cc-pi calculus in which the alternatives in a choice rather than being selected non-deterministically have a dynamic priority. Basically, a guard cj:?j in a choice is enabled if the constraint cj is entailed by the store of constraints and the prefix ?j can be consumed. Moreover, the j-th branch can be selected not only if the corresponding guard cj:?j is enabled but also if cj is weaker than the constraints ci of the other enabled alternatives. We prove that our choice operator is more general than a choice operator with static priority. Finally, we exploit some examples to show that our prioritised calculus allows arbitrarily complex QoS negotiations and that a static form of priority is strictly less expressive than ours.
EP  - 24
ID  - eprints114
PB  - Elsevier
JF  - Journal of Logic and Algebraic Programming
IS  - 1
AV  - none
N1  - Copyright © 2010 Elsevier Inc. All rights reserved. 
The 2nd Workshop on Formal Languages and Analysis of Contract-Oriented Software (FLACOS?08) 
SP  - 13
TI  - QoS Negotiation in Service Composition
VL  - 80
Y1  - 2011///
UR  - http://www.sciencedirect.com/science/article/B6W8D-4YWC12P-1/2/fba4154ba8acf9941004daea9925e884
A1  - Buscemi, Maria Grazia
A1  - Montanari, Ugo
KW  - Process calculi; Service oriented computing; Constraint-based models
ER  -