The increasing demand for Web services encourages commercial cloud service providers to publish their own services with various functional and nonfunctional capabilities in different cloud platforms. The aggregation of atomic services from multiple service repositories is the main idea of the service composition concept in multiclouds. The cloud Web service composition is a suitable way for satisfying users’ complex requests by integrating services from different clouds in order to create a new value-added composite service. The time required to serve a composite service by a multicloud environment is an important parameter, which depends on different factors, ranging from the service composition and selection algorithm to the number of atomic services published in the clouds. In this paper, a model based on timed colored Petri nets (TCPNs) is proposed to evaluate the service composition in multicloud environments while minimizing the number of clouds involved in serving a composite service request. The proposed TCPN graphically models the process of request submission, composite service analysis, service selection, and service provisioning in a multicloud environment. It also assesses both mean response time of the environment and probability of dropping composite requests. The verification of the accuracy of the proposed model is done by comparing the results obtained from the TCPN model, in two different scenarios, with the results from the CloudSim framework. These results confirm that our proposed TCPN model can appropriately model the system and evaluate its performance more efficiently than the CloudSim.

中文翻译：

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使用定时彩色 Petri 网对商业多云中的服务组合进行建模和评估

对 Web 服务不断增长的需求促使商业云服务提供商在不同的云平台上发布具有各种功能和非功能能力的服务。来自多个服务存储库的原子服务的聚合是多云中服务组合概念的主要思想。云Web服务组合是通过集成来自不同云的服务来创建新的增值组合服务来满足用户复杂请求的合适方式。多云环境为复合服务提供服务所需的时间是一个重要参数，它取决于不同的因素，从服务组合和选择算法到云中发布的原子服务数量。在本文中，提出了一种基于定时彩色 Petri 网 (TCPN) 的模型来评估多云环境中的服务组合，同时最大限度地减少服务于复合服务请求所涉及的云数量。提议的 TCPN 以图形方式对多云环境中的请求提交、复合服务分析、服务选择和服务供应过程进行建模。它还评估环境的平均响应时间和丢弃复合请求的概率。通过将 TCPN 模型在两种不同场景中获得的结果与 CloudSim 框架的结果进行比较，来验证所提出模型的准确性。这些结果证实，我们提出的 TCPN 模型可以适当地对系统建模并比 CloudSim 更有效地评估其性能。