The verification of the Cloud composite services’ correctness is challenging. In fact, multiple component services, derived from different Cloud providers with different service description languages and communication protocols, are involved in the composition which may raise incompatibility issues that in turn lead to a non-consistent composition. In this work, we propose a formal approach to model and verify Cloud composite services. Four verification levels are considered in this article; the structural, semantic, behavioral, and resource allocation levels. Therefore, we opted for the Event-B formal method that enables complex problems decomposition thanks to its refinement capabilities. The proposed approach has proven its efficiency for the modelling and verification of Cloud composite services. The proposed model comprises four abstract levels with respect to the four verification axes. A proof-based approach is applied to the model’s verification. We also succeeded in the validation of the model thanks to the model animation provided by the PROB tool. The use of formal methods provides a rigorous reasoning and mathematical proofs on the correction of the model which ensures the elaboration of correct-by-construction composite services.

中文翻译：

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一种基于 Event-B 的云复合服务验证方法

云组合服务的正确性验证具有挑战性。事实上，来自不同云提供商的多个组件服务，具有不同的服务描述语言和通信协议，都参与了组合，这可能会引发不兼容问题，进而导致组合不一致。在这项工作中，我们提出了一种形式化的方法来建模和验证云复合服务。本文考虑了四个验证级别；结构、语义、行为和资源分配级别。因此，我们选择了 Event-B 形式化方法，由于它的细化能力，它可以实现复杂问题的分解。所提出的方法已经证明了其对云复合服务的建模和验证的效率。所提出的模型包括关于四个验证轴的四个抽象级别。基于证明的方法应用于模型的验证。得益于 PROB 工具提供的模型动画，我们也成功地验证了模型。形式化方法的使用为模型的修正提供了严格的推理和数学证明，从而确保了构建正确的复合服务的精细化。