Abstract
With the progress of web technologies, web services with abundant functionalities, such as video transmission, location, navigation, etc., are becoming more and more pervasive. Automatic web service composition aims to automatically combine selected elementary web services from a finite service set by matching the input and output parameters given an initial state and a goal state. Considering the end-to-end Quality-of-Service(QoS) of each web service, the service composition problem becomes an optimization problem to find the optimal solution. This paper maps this problem to an automatic planning problem and proposes Q-Graphplan based on the classical graphplan, an efficient planner for solving classical planning problems. First, we construct a planning graph based on the dependency relationships of the web services and extract essential heuristics according to the reachability analysis. Second, we convert this planning graph to a directed path generation graph. Finally, we extract the optimal solution from the path generation graph using a backward A* algorithm with the heuristics of the planning graph. Furthermore, our approach avoids redundancies when constructing the planning graph and improves the searching effectiveness in extracting solution. We conduct experiments on the WSC-2009 dataset to compare performance against present approaches, and the results show the efficiency and effectiveness of our proposed approach.
Highlights
Since the development of the internet has been accelerating in recent years, web services are becoming more and more pervasive in people’s daily lives [1]
We study the multi-objective optimization in quality of service (QoS)-aware automatic service composition (ASC) problem with the dynamic model and apply the planning graph as a dependency analyzer and the heuristic generator to solve the problem
Each test set consists of four files: a WSDL file, describing services of the registry by their inputs/outputs, hierarchically organized in terms of concepts using an ontology recorded in an OWL file, a WSLA file, storing the QoS criteria values of each service, and an XML file storing the inputs and outputs of the query associated with the service registry
Summary
Since the development of the internet has been accelerating in recent years, web services are becoming more and more pervasive in people’s daily lives [1]. The first could be characterized as the static model, separately constructing an abstract service workflow and determining the atomic service via optimization algorithms to find solutions with optimal or near-optimal QoS values This model transforms the ASC problem as an integer programming problem, an NP-hard problem [16]–[20]. We study the multi-objective optimization in QoS-aware ASC problem with the dynamic model and apply the planning graph as a dependency analyzer and the heuristic generator to solve the problem. We use the admissible heuristics extracting from the planning graph and propose a backward A* algorithm to search optimal solution from the directed path generation graph.
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