Liangzhao Zeng, Boualem Benatallah, et.al. QoS-Aware Middleware for Web Services Composition, TOSE, 2004
这篇是WWW03的扩展版本, 两篇论文主体内容差不多, 不过许多地方要比WWW03写的更清楚明白完整(毕竟是TOSE上的文章).
1. 本文介绍了支持QoS driven Web service composition的middleware Agflow, 主要创新点有
1) 提出了一套Web Service Quality Model(Execution Price, Execution Duration, Reputation, Successful execution rate, availability), 可描述单个WS, 以及对组合服务QoS的聚合方法(基于Execution Path)
2) 提出了两类QoS-Driven Service Selection方法: (S4.1)是基于local optimization, 针对单个WS, 先将QoS值归一化处理, 然后使用SAW方法进行评估, 这个比较简单. (S4.2)是基于global planning, 主要内容跟WWW03里的基本一样, 先讨论单个的Execution Path, 然后讨论Multiple Execution Path, 最后提出用Integer Programming(IP)方法来求解.
3) 另外, (S4.2.5)中讨论了在运行时, Execution Plan中正在运行或将要运行的WS发生变化时(比如unavailable, QoS change), 需要进行replanning. Replanning的过程与一开始的global planning类似, 不同的是此时已执行的WS的QoS的数据是已知的, 正在正常运行的WS不能被替换.
2. 本文提到的一些assumption
1) "we assume that when the execution of noncritical services is not successful, the task can be re-executed without delaying the whole composite service execution."
2) "we assume that, when the noncritical service is unavailable, a service can be reselected without delaying the whole composite service execution;"
3. 摘录
(S4.2.3) "It can be proven that any arbitrary statechart can be transformed into an equivalent statechart in which the cycles do not cross the boundaries of conditional branches"
4. 其他
(S6 Experimentation) 没有看过