Efficient service composition in real time, while satisfying desirable Quality of Service (QoS) guarantees for the composite solution has been one of the topmost research challenges in the domain of services computing. On one hand, optimal QoS aware service composition algorithms, that come with the promise of solution optimality, are inherently compute intensive, and therefore, often fail to generate the optimal solution in real time for large scale web services. On the other hand, heuristic solutions that have the ability to generate solutions fast and handle large and complex service spaces, settle for sub-optimal solution quality. The problem of balancing the trade-off between computation efficiency and optimality in service composition has alluded researchers since quite some time, and several proposals for taming the scale and complexity of web service composition have been proposed in literature. In this paper, we present a new perspective towards this trade-off in service composition based on abstraction refinement, which can be seamlessly integrated on top of any off-the-shelf service composition method to tackle the space complexity, thereby, making it more time and space efficient. Instead of considering services individually during composition, we propose a set of abstractions and corresponding refinements to form service groups based on functional characteristics. The composition and QoS satisfying solution construction steps are carried out in the abstract service space. Our abstraction refinement methods give a significant speed-up compared to traditional composition techniques, since we end up exploring a substantially smaller space on average. Experimental results on benchmarks show the efficiency of our proposed mechanism in terms of time and the number of services considered for building the QoS satisfying composite solution.

中文翻译：

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使用抽象细化的 QoS 约束大规模 Web 服务组合

实时高效的服务组合，同时满足复合解决方案的理想服务质量 (QoS) 保证一直是服务计算领域的首要研究挑战之一。一方面，具有解决方案最优性承诺的最优 QoS 感知服务组合算法本质上是计算密集型的，因此通常无法为大规模 Web 服务实时生成最优解决方案。另一方面，能够快速生成解决方案并处理大型复杂服务空间的启发式解决方案，会满足于次优解决方案质量。在服务组合中平衡计算效率和最优性之间的权衡问题已经暗示研究人员很长一段时间了，并且在文献中已经提出了一些用于控制 Web 服务组合的规模和复杂性的建议。在本文中，我们提出了一种基于抽象细化的服务组合权衡的新视角，它可以无缝集成到任何现成的服务组合方法之上以解决空间复杂性，从而使其更时间和空间效率。我们不是在组合过程中单独考虑服务，而是提出了一组抽象和相应的细化，以根据功能特征形成服务组。在抽象服务空间中进行组合和满足 QoS 的解决方案构建步骤。与传统的合成技术相比，我们的抽象细化方法显着加快了速度，因为我们最终平均探索了一个小得多的空间。基准测试的实验结果表明，我们提出的机制在构建满足 QoS 的复合解决方案时考虑的时间和服务数量方面的效率。