[论文笔记]Combining Global Optimization with Local Selection for Efficient QoS-aware Service Composition (WWW 2009)"

Time Spended: 4.5 hours
第一作者的publication list如下(dblp):
Mohammad Alrifai(L3S Research Center, University of Hannover) and Thomas Risse.  Combining Global Optimization with Local Selection for Efficient QoS-aware Service Composition, WWW, 2009
Mohammad Alrifai: Distributed and Scalable QoS Optimization for Dynamic Web Service Composition. ICSOC PhD Symposium 2008
Mohammad Alrifai, Wolf-Tilo Balke, Peter Dolog, Wolfgang Nejdl: Nonblocking Scheduling for Web Service Transactions. ECOWS 2007: 213-222
Mohammad Alrifai, Peter Dolog, Wolfgang Nejdl: Transactions Concurrency Control in Web Service Environment. ECOWS 2006: 109-118

   基于QoS的服务选择可分为local selection和global selection, 这两种方法都有一些缺点, 前者是无法获得最优解, 后者存在性能问题(NP难).
本文作者认为: 在可接受的代价下找到没有明显违反QoS约束的服务要比花费很高代价来获得最优解更为重要, 基于此想法提出了一种"combines global optimization with local selection techniques"的服务选择方法. 核心思想是将global QoS constraints分解成local constraints, 使用的是MIP方法, 得到的是近似解.由于获得了local constraints, 可适用分布式场景中(没有中心管理节点)进行服务选择, 可扩展性更好.
   这篇论文针对的是服务组合的经典问题, 技术方案也算不上重大创新(创新点主要在4.1), 而且只针对服务组合中最简单的结构(sequential)进行讨论, 做为一篇WWW的论文, 感觉有点偏弱.

本文的assumptions & limitations & simplifications
(1) we assume that we have a universe of web services S which is defined as a union of abstract service classes.(S3)
(2) assume that information about service classes is managed by a set of service brokers.(S3)
(3) the number of service candidates per class l, which we assume to be equal for all classes. (S5.1)
(4) we consider quantitative non-functional properties  of web services(只考虑可量化, 可用实数表示的QoS属性) (S3.2)
(5) For the sake of simplicity, in this paper we consider only negative attributes (S3.2)
(6) In this paper, we focus on the sequential composition model. Other models may be reduced or transformed to the sequential model.(S3.3)