Formal Mapping of WSLA Contracts on Stochastic Models

  • Rouaa Yassin Kassab
  • Aad van Moorsel
Part of the Lecture Notes in Computer Science book series (LNCS, volume 6977)


Service level agreement (SLA) specification languages are designed to express monitorable contracts between service providers and consumers. It is of interest to determine if predictive models can be derived for SLAs expressed in such languages, if possible in automated fashion. For this purpose, we study in this paper the mapping of the Web Service Level Agreement (WSLA) into reward metrics defined in the Stochastic Discrete Event Systems (SDES) formalism. We associate a formal semantics with WSLA elements and map these on SDES through a five step mapping process, which includes expressions for the metrics and functions on these metrics, the time at which to predict, and the ultimate service level compliance probability. We illustrate our approach through a stock quote web service example.


Service Level Agreement Observation Interval Validity Period Evaluation Interval Reward Variable 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


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  1. 1.
    Molina-Jiménez, C., Pruyne, J., van Moorsel, A.: The role of agreements in IT management software. In: de Lemos, R., Gacek, C., Romanovsky, A. (eds.) Architecting Dependable Systems III. LNCS, vol. 3549, pp. 36–58. Springer, Heidelberg (2005)CrossRefGoogle Scholar
  2. 2.
    Sahai, A., Machiraju, V., Sayal, M., van Moorsel, A., Casati, F.: Automated SLA monitoring for web services. In: Feridun, M., Kropf, P.G., Babin, G. (eds.) DSOM 2002. LNCS, vol. 2506, pp. 28–41. Springer, Heidelberg (2002)CrossRefGoogle Scholar
  3. 3.
    Ludwig, H., Keller, A., Dan, A., King, R., Franck, R.: Web Service Level Agreement (WSLA) Language Specification. IBM (January 2003)Google Scholar
  4. 4.
    Andrieux, A., Czajkowski, K., Dan, A., Keahey, K., Ludwig, H., Nakata, T., Pruyne, J., Rofrano, J., Tuecke, S., Xu, M.: Web Services Agreement Specification (WS-Agreement). Open Grid Forum, version 2005/09 editionGoogle Scholar
  5. 5.
    Davide Lamanna, D., Skene, J., Emmerich, W.: SLAng: A language for defining service level agreements. In: The Ninth IEEE Workshop on Future Trends of Distributed Computing Systems, pp. 100–106 (2003)Google Scholar
  6. 6.
    Paschke, A., Schnappinger-Gerull, E.: A categorization scheme for SLA metrics. In: Service Oriented Electronic Commerce, pp. 25–40 (2006)Google Scholar
  7. 7.
    Zimmermann, A.: Stochastic Discrete Event Systems: Modeling, Evaluation, Applications. Springer-Verlag New York, Inc., Secaucus (2007)zbMATHGoogle Scholar
  8. 8.
    Dingle, N.J., Knottenbelt, W.J., Wang, L.: Service level agreement specification, compliance prediction and monitoring with performance trees. In: 22nd Annual European Simulation and Modelling Conference (ESM 2008), pp. 137–14 (September 2008)Google Scholar
  9. 9.
    Kassab, R.Y., van Moorsel, A.: Mapping WSLA on reward constructs in Möbius. In: 24th UK Performance Engineering Workshop, pp. 137–147 (2008)Google Scholar
  10. 10.
    Sanders, W.H.: Möbius User Manual, Version 2.3.1. University of Illinois, US (May 2010)Google Scholar
  11. 11.
    Sanders, W.H., Meyer, J.F.: A unified approach for specifying measures of performance, dependability, and performability. Dependable Computing and Fault-Tolerant Systems: Dependable Computing for Critical Applications 4, 215–237 (1991)CrossRefGoogle Scholar
  12. 12.
    Berglund, A., Boag, S., Chamberlin, D., Fernández, M.F., Kay, M., Robie, J., Simon, J.: XML path language (XPath) 2.0. Technical report, World Wide Web Consortium (January 2007)Google Scholar
  13. 13.
    Altova XMLSpy v2011r3 enterprise edition (2011),
  14. 14.
    Keller, A., Ludwig, H.: The WSLA framework: Specifying and monitoring service level agreements for web services. J. Netw. Syst. Manage. 11(1), 57–81 (2003)CrossRefGoogle Scholar
  15. 15.
    Ludwig, H., Keller, A., Dan, A., King, R., Franck, R.: A service level agreement language for dynamic electronic services 3, 43–59 (January 2003)Google Scholar
  16. 16.
    Grinstead, C.M., Snell, J.L.: Introduction to probability. American Mathematical Society, Providence (1997)zbMATHGoogle Scholar
  17. 17.
    Sanders, W.H., Meyer, J.F.: Stochastic activity networks: Formal definitions and concepts. In: European Educational Forum, pp. 315–343 (2000)Google Scholar
  18. 18.
    Thomas, J.P., Thomas, M., Ghinea, G.: Modeling of web services flow. In: CEC, pp. 391–398 (2003)Google Scholar

Copyright information

© Springer-Verlag Berlin Heidelberg 2011

Authors and Affiliations

  • Rouaa Yassin Kassab
    • 1
  • Aad van Moorsel
    • 1
  1. 1.School of Computing ScienceNewcastle UniversityUK

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