基于遗传算法的QoS感知的Web服务选择

提出一种用于QoS感知的Web服务选择的遗传算法．该算法采用关系矩阵编码方式,克服了一维编码方式表示的局限性,并且可以通过简单的方法来表示组合服务重计划及Web服务循环路径等情况,通过该算法一次运行,就可以从所有组合路径的组合方案中选出满足用户QoS需求的组合方案,而一维编码遗传算法在多路径情况下需多次编码、多次运行．算法还采用一种变异策略来提高算法的适应度．通过仿真比较,关系矩阵编码遗传算法比一维编码遗传算法获得了更优解,变异策略在提高算法适应度方面也发挥了作用．

Genetic Algorithm on Web Services Selection Supporting QoS

A novel genetic algorithm is presented for Quality of Service (QoS)-aware Web services selection. The genetic algorithm includes a special relation matrix coding scheme of chromosomes that can express simultaneously all of composite paths, which can not be expressed simultaneously by the one dimension coding scheme. This matrix can also represent effectively the composite service re-planning and cyclic paths with the help of a simple method. Many composition scenarios can also be showed by the matrix but not by the one dimension. Elements along the main diagonal of the matrix are used to represent all tasks in all of composite paths and others elements in the matrix for the direct relationship between every two tasks. The proposed genetic algorithm running only once can construct the composite service plan according with the QoS requirements from a great deal of services compositions with different QoSes. Meanwhile, the algorithm adopts a mutation policy to improve the fitness. Experiments on QoS-aware Web services selection show that the genetic algorithm with this matrix can get more excellent composite service plan than the genetic algorithm with the one dimension coding scheme, and that the mutation policy plays a role at the improvement of the genetic algorithm fitness.