Efficient Composition of Semantic Web Services with End-to-End QoS Optimization

Abstract

The efficiency of QoS-aware service composition is important since most service composition problems are known to be NP-hard. With the growing number of Web services, service composition is like a decision problem on selecting services or/and execution plans to satisfy the users end-to-end QoS requirements (e.g. response time, throughput). Composite services with the same functionality may have different execution plans, which may cause different end-to-end QoS. A model combining semantic data-links and QoS is proposed, which leads to an efficient approach to automatic construction of a composite service with optimal end-to-end QoS. The approach is based on a greedy algorithm to select both services and execution plans for composite services. Empirical and theoretical analysis of the approach show that its time complexity is $O({\mathit{mn}}^{2})$ for a repository with n services and an ontology with m concepts. Moreover, the approach takes linear time in practice when using an index to search services in the repository.