A probabilistic approach to modeling and estimating the QoS of web-services-based workflows

San Yih Hwang, Haojun Wang, Jian Tang, Jaideep Srivastava

Research output: Contribution to journalArticlepeer-review

196 Scopus citations


Web services promise to become a key enabling technology for B2B e-commerce. One of the most-touted features of Web services is their capability to recursively construct a Web service as a workflow of other existing Web services. The quality of service (QoS) of Web-services-based workflows may be an essential determinant when selecting constituent Web services and determining the service-level agreement with users. To make such a selection possible, it is essential to estimate the QoS of a WS workflow based on the QoSs of its constituent WSs. In the context of WS workflow, this estimation can be made by a method called QoS aggregation. While most of the existing work on QoS aggregation treats the QoS as a deterministic value, we argue that due to some uncertainty related to a WS, it is more realistic to model its QoS as a random variable, and estimate the QoS of a WS workflow probabilistically. In this paper, we identify a set of QoS metrics in the context of WS workflows, and propose a unified probabilistic model for describing QoS values of a broader spectrum of atomic and composite Web services. Emulation data are used to demonstrate the efficiency and accuracy of the proposed approach.

Original languageEnglish (US)
Pages (from-to)5484-5503
Number of pages20
JournalInformation Sciences
Issue number23
StatePublished - Dec 1 2007

Bibliographical note

Funding Information:
This work was partially supported by “Aim for the Top University Plan” of the National Sun Yat-sen University and Ministry of Education, Taiwan, ROC.


  • QoS aggregation
  • Structural workflow
  • Web service QoS
  • Web service composition
  • Web services
  • Workflow QoS


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