We report on our use of quantitative modelling in predicting the success of systems and services in achieving Service Level Agreements (SLAs). We construct models of the systems in the stochastic process algebra PEPA, and queries in the language of eXtended Stochastic Probes (XSP). The query and model together are translated into an underlying continuous time Markov chain (CTMC) which is evaluated in order to assess the SLA. This most often requires a passage-time analysis where a passage (sequence of activity observations) is specified and the numerical analysis returns a function mapping the probability of completing the passage against time since the passage was initiated.
|Title of host publication||Rigorous Software Engineering for Service-Oriented Systems|
|Subtitle of host publication||Results of the SENSORIA Project on Software Engineering for Service-Oriented Computing|
|Editors||Martin Wirsing, Matthias Hoelzl|
|Number of pages||19|
|Publication status||Published - 2011|
|Name||Lecture Notes in Computer Science|
|Publisher||Springer Berlin / Heidelberg|