Cloud computing has emerged as a promising platform for running scientific workflows across various domains. Scientists can take advantage of different cloud service models, such as serverful or serverless, to execute workflows based on their specific requirements, along with diverse pricing models like on-demand, reserved, or spot instances to reduce execution costs. However, the challenge of selecting appropriate resources and pricing models, coupled with the orchestration and scheduling of workflow tasks, creates significant complexity for users. To mitigate this burden, Workflow as a Service (WaaS) brokers have been introduced to facilitate workflow execution. In recent years, numerous studies have been published, either directly or indirectly related to this research area, highlighting the need for a comprehensive and systematic review of WaaS brokers to identify key trends and challenges in this field. In this paper, we conduct a Systematic Mapping Study (SMS) on WaaS brokers within cloud environments. The SMS employs a thorough 3-tier strategy (database search, backward snowballing, and forward snowballing) to answer five research questions. A total of 87 high-quality articles, published in 49 prestigious venues, are analyzed to derive a taxonomy based on the architecture of WaaS brokers. The articles are classified and surveyed according to this taxonomy, and future research directions for the design and implementation of WaaS brokers are explored. This study provides valuable insights for researchers and developers, helping them identify major trends and issues in the field of WaaS brokers.

翻译：云计算已成为跨领域运行科学工作流的有前景平台。科学家可根据具体需求，利用无服务器或服务器化等不同云服务模型执行工作流，并采用按需、预留或竞价实例等多样化定价模式以降低执行成本。然而，选择合适的资源与定价模型的挑战，以及工作流任务的编排调度问题，给用户带来了巨大复杂性。为减轻这一负担，工作流即服务中介被引入以促进工作流执行。近年来，该领域发表了大量直接或间接相关的研究成果，凸显了开展全面系统综述以识别关键趋势与挑战的必要性。本文对云环境中的工作流即服务中介进行了系统映射研究。该研究采用三层策略（数据库检索、后向滚雪球、前向滚雪球）全面回答五个研究问题。共分析来自49个知名学术平台的87篇高质量文献，基于工作流即服务中介架构构建分类体系，并依此对文献进行分类综述，探讨了工作流即服务中介设计与实现的未来研究方向。本研究为研究人员与开发者提供了宝贵见解，助力其把握工作流即服务中介领域的主要趋势与关键问题。