On repairing queries in cloud computing

Cloud Computing based Software as a Service (SaaS) combines multiple Web Services to satisfy a SaaS request, therefore SaaS should be able to dynamically seek replacements for faulty or underperforming services, thus performing self-healing. However, it may be the case of available services that do not match all user's request, leading the system to grind to a halt. It is better to have an alternative candidate in the cloud while not fulfilling all the constraints. In this paper, we provide a solution to repair the failed user's query by rewriting it with an approximation. It is based on a Minimally Unsatisfiable Subformula (MUS) that exploits Satisfiability (SAT) problem to repair the query and provide an alternative SaaS that leads to a successful request closed to the original one.