International Journal of Web Applications Khalid Mansour 12 2 2020 https://doi.org/10.6025/ijwa/2020/12/2/37-46 http://www.dline.info/ijwa/fulltext/v12n2/ijwav12n2_1.pdf Web service composition is about maximizing the benefits of different Web services by combining a certain number of Web services to deliver a fully end-to-end service. This paper presents a systematic review of the two major trends of Web service compositions: top-down composition and bottom-up composition. The top-down composition starts with a well defined goal and search criteria. On the other hand, the goal and search criteria in the bottom-up composition are not well defined. The bottom-up composition is often called Web service mining. Web service mining is a new trend that aims at discovering useful and interesting compositions of existing Web services.