Abstract
Introduction. Cloud–Computing [1] was considered as a revolution. Taking its root in distributed systems design, this paradigm advocates the share of distributed computing resources designated as “the cloud”. The main advantage of using a cloud-based infrastructure is the associated scalability property (called elasticity). Since a cloud works on a pay–as–you–go basis, companies can rent computing resources in an elastic way. A typical example is to temporary increase the server–side capacity of an e–commerce website to avoid service breakdowns during a load peak (e.g., Christmas period). However, there is still a huge gap between the commercial point of view and the technical reality that one has to face in front of “the cloud”. As any emerging paradigm, and despite all its intrinsic advantages, Cloud–Computing still relies on fuzzy definitions1 and lots of buzzwords (e.g., the overused “IaaS”, “PaaS” and “SaaS” acronyms that does not come with accepted definitions).