Modelling with Generalized Stochastic Petri Nets
Modelling with Generalized Stochastic Petri Nets
The WSLA Framework: Specifying and Monitoring Service Level Agreements for Web Services
Journal of Network and Systems Management
ICATPN '97 Proceedings of the 18th International Conference on Application and Theory of Petri Nets
QoS-Aware Middleware for Web Services Composition
IEEE Transactions on Software Engineering
Applying model checking to BPEL4WS business collaborations
Proceedings of the 2005 ACM symposium on Applied computing
Formal semantics and analysis of control flow in WS-BPEL
Science of Computer Programming
Probabilistic QoS and Soft Contracts for Transaction-Based Web Services Orchestrations
IEEE Transactions on Services Computing
Event structure semantics of Orc
WS-FM'07 Proceedings of the 4th international conference on Web services and formal methods
A language for task orchestration and its semantic properties
CONCUR'06 Proceedings of the 17th international conference on Concurrency Theory
Critical Paths in the Partial Order Unfolding of a Stochastic Petri Net
FORMATS '09 Proceedings of the 7th International Conference on Formal Modeling and Analysis of Timed Systems
QoS-aware management of monotonic service orchestrations
Formal Methods in System Design
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Web Service orchestrations are compositions of different Web Services to form a new service. The services called during the orchestration guarantee a given Quality of Service (QoS) to the orchestrator, usually in the form of contracts. These contracts can then be used by the orchestrator to deduce the contract it can offer to its own clients, by performing contract composition. An implicit monotonicity assumption in contract based QoS management is: "the better the component services perform, the better the orchestration's performance will be". In some orchestrations, however, monotonicity can be violated, i.e., the performance of the orchestration improves when the performance of a component service degrades. This is highly undesirable since it can render the process of contract composition inconsistent. In this paper we formally define monotonicity for orchestrations modelled by Colored Occurrence Nets (CO-nets) and we characterize the classes of monotonic orchestrations. Contracts can be formulated as hard, possibly nondeterministic, guarantees, or alternatively as probabilistic guarantees. Our work covers both cases. We show that few orchestrations are indeed monotonic, mostly because of complex interactions between control, data, and timing. We also provide user guidelines to get rid of non-monotonicity when designing orchestrations.