The vendor lock‐in is a prominent issue in cloud computing. It is caused by cloud providers who offer proprietary services, which hinders the cloud interoperability. Client‐centric interoperability enables the migration of the data and applications across clouds; it gives the clients control over their workloads and a wider range of service choices. Whereas, provider‐centric interoperability allows the providers to collaborate. Thus, providers, who have spare resources, can lend them to other providers who lack computational or storage capabilities to overcome the limitations of their local resources. In this article, we conduct a survey to differentiate between client‐ and provider‐centric interoperability solutions. We aim to provide an up‐to‐date analysis of the current tendencies and the neglected areas of the cloud interoperability field. Thus, we study the cloud service interoperability evolution through the years. Furthermore, we propose definitions for the intra‐cloud and inter‐cloud interoperability. Moreover, we propose a taxonomy to classify the cloud interoperability approaches into client‐centric and provider‐centric categories. Then, for each category, we classify the approaches based on their interoperability environment into single cloud or interconnected clouds. Finally, we analyze and compare the approaches based on multiple criteria. The study reveals the focus on the client‐centric solutions and the interoperability in interconnected clouds. We notice more interest in the data and application levels interoperability, mainly, in infrastructure as a service model. We also find that client‐centric solutions are, mostly, semantic technologies and brokers. However, provider‐centric solutions are middleware, protocols, and standards. We conclude that a generic cloud service interoperability model is needed.

中文翻译：

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云计算中服务互操作性调查：以客户为中心和以供应商为中心的视角

供应商锁定是云计算中的一个突出问题。它是由提供专有服务的云提供商造成的，这阻碍了云互操作性。以客户端为中心的互操作性支持跨云迁移数据和应用程序；它使客户能够控制他们的工作负载和更广泛的服务选择。而以提供商为中心的互操作性允许提供商进行协作。因此，拥有空闲资源的供应商可以将它们借给缺乏计算或存储能力的其他供应商，以克服其本地资源的局限性。在本文中，我们进行了一项调查，以区分以客户为中心和以提供商为中心的互操作性解决方案。我们旨在提供对云互操作性领域的当前趋势和被忽视领域的最新分析。因此，我们研究了这些年来云服务互操作性的演变。此外，我们提出了云内和云间互操作性的定义。此外，我们提出了一种分类法，将云互操作性方法分为以客户为中心和以提供商为中心的类别。然后，对于每个类别，我们根据其互操作性环境将方法分类为单一云或互连云。最后，我们分析和比较基于多个标准的方法。该研究揭示了对以客户端为中心的解决方案和互连云中的互操作性的关注。我们注意到对数据和应用程序级别的互操作性更感兴趣，主要是基础设施即服务模型。我们还发现以客户为中心的解决方案主要是语义技术和代理。然而，以供应商为中心的解决方案是中间件、协议和标准。我们得出结论，需要一个通用的云服务互操作性模型。