Defining and guaranteeing dynamic service levels in clouds

In this paper, we introduce SLAC, a SLA definition language specifically devised for clouds as a formalism to support the whole SLA lifecycle. The main novelty of the language is the possibility of capturing within the SLA the dynamic aspects of the environment by defining the conditions and actions to change service levels at runtime. SLAC permits to make the most of cloud elasticity, reduces the need for renegotiation and provides guarantees for dynamic scenarios. The language has formal syntax and semantics, and it comes with effective software tools supporting the whole SLA management lifecycle. The impact of our language and of its software tools is assessed by considering a series of experiments that provide empirical evidences of the advantages of SLAC.