An Initial Approach to Explaining SLA Inconsistencies

  • Carlos Müller
  • Antonio Ruiz-Cortés
  • Manuel Resinas
Part of the Lecture Notes in Computer Science book series (LNCS, volume 5364)


An SLA signed by all interested parties must be created carefully, avoiding contradictions between terms, because their terms could carry penalties in case of failure. However, this consistency checking may become a challenging task depending on the complexity of the agreement. As a consequence, an automated way of checking the consistency of an SLA document and returning the set of inconsistent terms of the agreement would be very appealing from a practical point of view. For instance, it enables the development of software tools that make the creation of correct SLAs and the consistency checking of imported SLAs easier for users. In this paper, we present the problem of explaining WS-Agreement inconsistencies as a constraint satisfaction problem (CSP), and then we use a CSP solver together with an explanation engine to check the consistency and return the inconsistent terms. Furthermore, a proof-of-concept using Choco solver in conjunction with the Palm explanation engine has been developed.


Service Level Agreement WS-Agreement Consistency Checking Debugging Quality of Service 


  1. 1.
    Choco constraint solver web site (2008),
  2. 2.
    OGF Grid Resource Allocation Agreement Protocol WG (GRAAP-WG). Web Services Agreement Specification (WS-Agreement), v. gfd.107 (2007)Google Scholar
  3. 3.
    Jussien, N., Barichard, V.: The PaLM system: explanation-based constraint programming. In: Proceedings of TRICS: Techniques foR Implementing Constraint programming Systems, a post-conference workshop of CP 2000, Singapore, September 2000, pp. 118–133 (2000)Google Scholar
  4. 4.
    Müller, C., Martín-Díaz, O., Ruiz-Cortés, A., Resinas, M., Fernández, P.: Improving Temporal-Awareness of WS-Agreement. In: Krämer, B.J., Lin, K.-J., Narasimhan, P. (eds.) ICSOC 2007. LNCS, vol. 4749, pp. 193–206. Springer, Heidelberg (2007)CrossRefGoogle Scholar
  5. 5.
    Oldham, N., Verma, K., Sheth, A., Hakimpour, F.: Semantic WS-Agreement Partner Selection. In: 15th International WWW Conf., pp. 697–706. ACM Press, New York (2006)Google Scholar
  6. 6.
    Ruiz-Cortés, A., Martín-Díaz, O., Durán, A., Toro, M.: Improving the Automatic Procurement of Web Services using Constraint Programming. Int. Journal on Cooperative Information Systems 14(4) (2005)Google Scholar
  7. 7.
    Schiex, T., Verfaillie, G.: Nogood recording for static and dynamic constraint satisfaction problems. In: Tools with Artificial Intelligence, TAI 1993. Proceedings, Fifth International Conference, November 8-11, 1993, pp. 48–55 (1993)Google Scholar
  8. 8.
    Tsang, E.: Foundations of Constraint Satisfaction. Academic Press, London (1995)Google Scholar

Copyright information

© Springer-Verlag Berlin Heidelberg 2008

Authors and Affiliations

  • Carlos Müller
    • 1
  • Antonio Ruiz-Cortés
    • 1
  • Manuel Resinas
    • 1
  1. 1.Dpto. Lenguajes y Sistemas InformáticosETS. Ingeniería Informática - Universidad de Sevilla (Spain - España)SevillaEspaña

Personalised recommendations