Specifying Compensations with WS‑Agreement

Abstract

During the last years the use of service level agreements (SLA) is rising uncontrollably to describe the rights and obligations of parties involved in service provisioning (typically the service consumer and the service provider); amongst other information, SLA could define guarantees associated with the idea of service level objectives (SLOs) that normally represent key performance indicators of either the consumer or the provider. In case the guarantee is under or over fulfilled SLAs could also define some compensations (i.e. penalties or rewards). In such a context, there have been important steps towards the automation of the analysis of SLAs. One of these steps is a characterization model of SLAs with compensations proposed by the authors in a previous work; and another step is the standardisation effort in the SLAs notation made by WS-Agreement. However, real-world SLAs includes complex concepts that must be considered, namely: (i) SLA terms that specify compensations without an explicit SLO; and (ii) a limit for the compensations. In this paper we extend our prior characterization model considering these complex concepts. Specifically, (i) we provide up to five real-world scenarios whose SLAs incorporate aforementioned new concepts; (ii) we extend our model for compensable guarantees considering terms without an explicit SLO; and (iii) we provide a novel WS-Agreement-based syntax to model SLAs with compensations considering these concepts. These contributions aim to establish a foundation to elaborate tools that could provide an automated support to model and analyse SLAs with compensations.