Web Service (WS) composition consists in combining several WSs into a Composite WS (CWS), which becomes a value-added process. In order to provide reliable and fault-tolerant CWSs, several transactional-aware composition approaches have been proposed. However, as far as we know, no real classification survey of such approaches exists. This is the contribution of this chapter. Our classification distinguishes the more relevant and recent propositions in two groups: approaches based on WS transactional properties and the ones also integrating QoS criteria to the composition process. All these studied approaches are compared according to several criteria: the transactional model used or proposed, the control flow model used or automatically generated, the mechanism proposed to verify the transactional property of the composition, the step(s) of the composition process involved in, and the protocols or the standard languages used or extended. This classification allows underlining the lacks and the future directions which should be studied.
Providing fault-tolerant execution of web-service-based workflows within clouds