[论文阅读] Dynamic Web service selection for reliable Web service composition (TSC, 2008)
Time: 2.9 hours
San-Yih Hwang, Ee-Peng Lim, Chien-Hsiang Lee, Cheng-Hung Chen, "Dynamic Web Service Selection for Reliable Web Service Composition," IEEE Transactions on Services Computing, vol. 1, no. 2, pp. 104-116, Apr.-June 2008, doi:10.1109/TSC.2008.2
作者San-Yih Hwang(黄三益), 台湾中山大学教授, 研究兴趣包括工作流管理等, 发表论文颇多, 部分相关论文列举如下:
2009, "Dynamic Web Service Selection for Reliable Web Service Composition," IEEE Transactions on Services Computing, 1(2), NSC 96-2752-H-110-005. "Selecting Web Services and Participants for Enforcing Workflow Access Control," Proc. of Hawaii International Conference on System Sciences (HICSS-42), Big Island, Hawaii. 2007. "A Probabilistic Approach to Modeling and Estimating the QoS of Web-services-based Workflows," Journal of Information Sciences (INS), 177(23), pp 5484-5503, SCI Expanded. 2007, "On Composing a Reliable Composite Web Service: A Study of Dynamic Web Service Selection," Proc. of 2007 International Conference on Web Services (ICWS2007), Salk Lake City, USA. 2004, "A Probabilistic QoS Model and Computation Framework for Web Services-Based Workflows," Proc. of the 23rd International Conference on Conceptual Modeling, (ER2004), Shanghai , China.
以下是论文笔记.
1. 本文的一个重要基础:
现有针对服务选择和组合的论文, 大多数将WS视为基本单元, 事实上一个WS可以包含多个opeartions, 并且对这些operations的调用是有限制的. 常见的限制有:
(1) separation of duties. 比如某两个operation不能由同一个WS完成, 以避免潜在的欺诈.
(2) binding of duities. 比如要求order和payment服务由同一个WS完成.
(3) 对operations调用顺序的约束.
为了表达出这种约束, 本文采用了FSM作为建模工具(使用FSM对WS进行建模不是作者首创, 之前也有相关论文). 对于每一个WS, 都有一个FSM(S3.1), 这个FSM的动作集是该WS的operations, 并定义了相应的状态集(包括初始和终结状态), 如果使用一个WS, 要求该服务最终处于终结状态.
2. 对于WSC常见的constraints, 作者归纳如下(S2.3):
(1) the atomicity (all or nothing) of each WS
(2) the compatibility of the constituent WSs
(3) QoS requirements
(4) all operation sequences of the composite WS must be captured
3. (S3) 本章详细介绍了使用FSM对WS和WS composition进行建模, 还举例说明了问题和答案的形式, 内容通俗易懂, 写的挺好. 详见论文.
4 摘录本文对经典论文Zeng03(WWW)和Yu07(TOW)的综述.
Zeng03:
To optimize the selection for the entire process, Zeng et al. proposed computing an optimal set of WSs for each possible execution path in the process based on a weighted combination of QoS measures. When it comes to deciding a WS for a given activity t, the most poplar execution path on which t appears is chosen, and the WS assigned to t in that path is selected. To speed up the computation, techniques of integer programming are employed. However, the number of possible execution paths could be huge, especially in the presence of a loop. Besides, the failure of WSs at runtime requires the recomputation of a set of new integer programs, which may not be feasible in practice.
Yu07:
… proposed a scheme to optimize the end-to-end QoS for various flow structures. They used a utility function derived from the QoS quality and formulated the optimization problem as a general flow problem.
5. 其他
(1)本文对reliability的定义:
"the probability that it successfully responds within a reasonable period of time."
(2) 文中提到FSM是最合适用来描述"operation orders in a WS"的形式化方法. 其他的形式化方法, 比如 Petri Net, process algebra 是否也可以用来描述这种关系? 不知道是否已有相关论文.
(3) 本文的方法对规模较小的服务组合适用, 规模太大时效率有问题(这大概也是基于FSM的方法具有的通病).
(3) 最近时间比较紧张, 剩下的几章(解决方法(S4), 原型开发(S5), 实验(S6)这次就先不看了. 这篇毕竟是transaction上的论文, 比较有内涵, 有时间还得细细品味.
