Hybrid Web Service Selection based on Functional and Non-Functional Properties Halfaoui Amal Computer science department Tlemcen university-Algeria a halfaoui@mail.univ-tlemcen.dz Hadjila Fethallah Computer science department Tlemcen university-Algeria f hadjila@mail.univ-tlemcen.dz Didi Fedoua Computer science department Tlemcen university-Algeria f didi@mail.univ-tlemcen.dz Abstract - Web service composition enables seamless and dynamic integration of business application on the web. The performance of the composed application is determined by the performance of the involved web services. Therefore, the selection of composite services is a very complex and challenging task, it becomes a decision problem on which component services should be selected so that user’s preferences are satisfied, especially when it has to consider not only the user’s QoS preferences (non-functional aspect) but also user’s functional Preferences (functional aspect). In this paper we address this problem and present a solution that combines local selection with global optimization. The proposed solution consists of two steps: First, in the local selection, we take into account both of users’ preferences and QoS requirements and use dominance relationship to select the top-k services and reduce the services involved in the composition. Second, we use a global optimization to fulfil the global requirement and select the Optimal composition by using the Tabu Search Algorithm. The experimental evaluation indicates that our approach significantly outperforms existing solutions in terms of optimality. Keywords - Web Services Selection, Optimization, Services Composition. 1 INTRODUCTION The Selection of an appropriate Web service for a particular task has become a difficult challenge due to the increasing number of Web services of- fering similar functionalities. The functional prop- ertie mtd mmmzmzmb s describe what the service can do and the non-functional properties depict how the service can do it. The requirements of the user are rarely satisfied by one web service but generally we need more than one. The web service com-position consists in building a value-added ser-vices and web applications by integrating and com- posing existing elementary web services. A lot of approaches have been proposed, they include AI planning techniques [15], formal models [7] (fi- nite states machines, petri nets,...) and meta- heuristics[8][19]. The majority of them does not address the functional, the non functional aspects and the global constraints in the same time. Our purpose is to take into account both of the two as- pects(functional, n-fonctional) and fulfill the global constraints. In order to explain our motivations let us consider the following example: The example [6] in Table-1 presents an e- commerce system supporting users to buy cars. Each service has its input i() and output o() pa- rameters. Services providing the same function- ality belong to the same class( S 21 ,S 22 ,S 23 belong to S 2 ). Each service has: i. Functional constraints on the data it manipulates, For instance the cars returned by S 22 have prices between 5500 and 7000 euro. ii. N-functional constraints, Services set their val- ues associated to three parameters q1,q2,q3 cor- responding to price, response time and availability. Suppose that a user x wants to buy a french car preferably at an affordable price[5000,7000] with warranty between 12 and 18 months, having a power [60,80] and consumption [10,11]. The user preference concern also the global constraints, like the total price of the composition don’t exceed 10 euro. The user will have to invoke S 11 , he can then invoke ICAASE'2014 Hybrid WebService Selection based on Functional and Non-Functional Properties International Conference on Advanced Aspects of Software Engineering ICAASE, November, 2-4, 2014, Constantine, Algeria. 20