Monotonicity in Service Orchestrations
PETRI NETS '09 Proceedings of the 30th International Conference on Applications and Theory of Petri Nets
A Probabilistic Approach to Service Selection with Conditional Contracts and Usage Patterns
ICSOC-ServiceWave '09 Proceedings of the 7th International Joint Conference on Service-Oriented Computing
CPN-TWS: a coloured petri-net approach for transactional-QoS driven Web Service composition
International Journal of Web and Grid Services
A tool for QoS probability distribution estimation of web service compositions
OTM'10 Proceedings of the 2010 international conference on On the move to meaningful internet systems
Pairwise testing of dynamic composite services
Proceedings of the 6th International Symposium on Software Engineering for Adaptive and Self-Managing Systems
Fuzzy conformance checking of observed behaviour with expectations
AI*IA'11 Proceedings of the 12th international conference on Artificial intelligence around man and beyond
Probability distribution-based QoS analysis for web service composition
WISS'10 Proceedings of the 2010 international conference on Web information systems engineering
A QoS evaluation method for personalized service requests
WISM'11 Proceedings of the 2011 international conference on Web information systems and mining - Volume Part II
QoS analysis for web service compositions based on probabilistic qos
ICSOC'11 Proceedings of the 9th international conference on Service-Oriented Computing
Optimizing decisions in web services orchestrations
ICSOC'11 Proceedings of the 9th international conference on Service-Oriented Computing
Time based qos modeling and prediction for web services
ICSOC'11 Proceedings of the 9th international conference on Service-Oriented Computing
A Survey of Web Services Provision
International Journal of Systems and Service-Oriented Engineering
Optimal Fault Tolerance Strategy Selection for Web Services
International Journal of Web Services Research
Service Oriented Computing and Applications
UsageQoS: Estimating the QoS of Web Services through Online User Communities
ACM Transactions on the Web (TWEB)
QoS-aware management of monotonic service orchestrations
Formal Methods in System Design
Information Sciences: an International Journal
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Service level agreements (SLAs), or contracts, have an important role in web services. They define the obligations and rights between the provider of a web service and its client, about the function and the Quality of the service (QoS). For composite services like orchestrations, contracts are deduced by a process called QoS contract composition, based on contracts established between the orchestration and the called web services. Contracts are typically stated as hard guarantees (e.g., response time always less than 5 msec). Using hard bounds is not realistic, however, and more statistical approaches are needed. In this paper we propose using soft probabilistic contracts instead, which consist of a probability distribution for the considered QoS parameter—in this paper, we focus on timing. We show how to compose such contracts, to yield a global probabilistic contract for the orchestration. Our approach is implemented by the TOrQuE tool. Experiments on TOrQuE show that overly pessimistic contracts can be avoided and significant room for safe overbooking exists. An essential component of SLA management is then the continuous monitoring of the performance of called web services, to check for violations of the SLA. We propose a statistical technique for run-time monitoring of soft contracts.