Cloud computing has been consolidated as a support for the vast majority of current and emerging technologies. However, there are some barriers that prevent the exploitation of the full potential of this technology. First, the major cloud providers currently put the onus of implementing the mechanisms that ensure compliance with the desired service levels on cloud consumers. However, consumers do not have the required expertise. Since each cloud provider exports a different set of low-level metrics, the strategies defined to ensure compliance with the established service-level agreement (SLA) are bound to a particular cloud provider. This fosters provider lock-in and prevents consumers from benefiting from the advantages of multi-cloud environments. This paper presents a solution to the problem of automatically translating SLAs into objectives expressed as metrics that can be measured across multiple cloud providers. First, we propose an intelligent knowledge-based system capable of automatically translating high-level SLAs defined by cloud consumers into a set of conditions expressed as vendor-neutral metrics, providing feedback to cloud consumers (intelligent tutoring system). Secondly, we present the set of vendor-neutral metrics and explain how they can be measured for the different cloud providers. Finally, we report a validation based on two use cases (IaaS and PaaS) in a multi-cloud environment formed by leading cloud providers. This evaluation has demonstrated that, thanks to the complementarity of the two solutions, cloud consumers can automatically and transparently exploit the multi-cloud in many application domains, as endorsed by the cloud experts consulted in the course of this study.

翻译：云计算已成为支撑当前及新兴主流技术的重要基础。然而，某些障碍限制了该技术潜力的充分发挥。首先，目前主要云服务提供商将确保服务等级协议（SLA）合规的机制实施责任转移至云消费者，但消费者往往缺乏必要的专业技术能力。由于各云服务商输出的底层指标集存在差异，为确保既定SLA合规而制定的策略必然绑定于特定云服务商，这不仅加剧了供应商锁定效应，也阻碍了消费者从多云环境中获益。本文提出了一种解决方案，能够自动将SLA转化为可在多云环境下测量的供应商中立指标。首先，我们设计了一种智能知识驱动系统，能够自动将云消费者定义的高层SLA转换为一组基于供应商中立指标的可度量条件，并为云消费者提供实时反馈（智能导学系统）。其次，我们构建了供应商中立指标集，并阐明如何在不同的云服务商环境中实现这些指标的测量。最后，我们通过在领先云服务商构成的多云环境中对两个用例（IaaS与PaaS）进行验证评估。实验表明，得益于两种解决方案的互补性，云消费者能够在众多应用领域中实现自动透明的多云资源利用，这一结论已获得本研究咨询的多位云领域专家的认可。