30 Int. J. Web Engineering and Technology, Vol. 13, No. 1, 2018 Copyright © 2018 Inderscience Enterprises Ltd. Q-DWSO: hybrid approach for QoS-aware dynamic web services orchestration Reena Gupta* School of Computer Science and Information Technology, Devi Ahilya Vishwavidyalaya, 452001, India Email: gupta.reena865@gmail.com *Corresponding author Raj Kamal School of Computer Science and Information Technology, Devi Ahilya Vishwavidyalaya, 452001, India and Prestige Institute of Engineering, Management and Research, Indore 452010, India Email: dr_rajkamal@hotmail.com Ugrasen Suman School of Computer Science and Information Technology, Devi Ahilya Vishwavidyalaya, 452001, India Email: ugrasen123@yahoo.com Abstract: Many complex business-applications require the composition of tasks invoking multiple web services. The complexity of a composition process increases when a composition needs dynamic functionalities. Web services (WSs) of different service providers can be functionally identical, but have varying Quality of Service (QoS) attributes. A QoS optimisation is thus required at every stage in a composite web service (CWS). Maximising the overall utility functions are the need at both, component and composition levels. Local (task level) or global (composition using tasks in CWS) optimisation is currently used approach during the composition from the tasks. The present paper proposes a hybrid approach using the local as well as global optimisations. While local optimisation ensures the composition from the WSs in the trustworthy environment, the global optimisation satisfies the QoS constraints at the global level. The approach uses a hybrid orchestration structure. It maximises overall utility functions and reduces computational time related complexity. Keywords: service oriented architecture; SOA; composite web service; CWS; web services composition; hybrid orchestration; quality of service; QoS; dynamic orchestration; composite service; computational time complexity; web-services local optimisation; web-services global optimisation; parallel web-services structure; sequential web-services structure.