More and more companies are currently migrating business processes to the Cloud in order to handle customer service in an efficient and cost effective way. Cloud Computing's elasticity and flexibility in service delivery makes it an ideal solution for companies to deal with highly variable service demands and uncertain financial environment to ensure the required QoS while using resources and reduce their expenses. Elasticity management is witnessing a lot of attention from IT community as a pivotal issue for finding the right tradeoffs between QoS levels and operational costs by working on developing novel methods and mechanisms. However, controlling business process elasticity and defining non-trivial elasticity strategies are challenging issues. In this paper, we propose an elasticity strategy description language, called Strat. It is defined as an extensible Domain-Specific Language to allow business process holders to describe elasticity strategies that are evaluated using our formal evaluation framework. Given a usage behavior and a business process, the evaluation consists in providing a set of plots that allows the analysis and the comparison of strategies. Our contributions and developments provide Cloud tenants with facilities to choose elasticity strategies that fit to their business processes and usage behaviors.