Transactional Composite Services Research Articles

A Correct-by-Construction Model for Verifying Transactional Composite Services Configuration

Reusability is a central concept of Web services as it allows for the construction of composite Web services at a lower cost/effort. Web services offer diverse functional capabilities (e.g., ticket purchase, hotel booking) and inherent transactional properties. However, due to the lack of an explicit and formal description of these functional and transactional perspectives, the correctness of the transactional reliability and functional properties cannot be verified. The composite Web service reliability is computed using a set of transactional requirements defined by designers throughout the Accepted Termination States (ATS) concept. The main objective of this article is to introduce a formal model of the Web service configuration and its correctness requirements that permit to ensure the correct Web service execution from functional and transactional points of view. For that purpose, we developed a Correct Configuration Model for Transactional Composite Services (CCM4TCS) using the <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Event-B</small> method. This model is used to formally validate the consistency of composite Web service configuration’s properties and requirements. It allows also to check the correctness of ATS constraints that we use as reliability parameters. The correctness and the validation of our model are ensured by discharging proof obligations and by animating the specification using the ProB model-checker.

An Active and Opportunistic Service Replacement Algorithm Orienting Transactional Composite Service Dynamic Adaptation

Various exceptions leading to the business process no response temporarily or service interruption are common in dynamic service environment,which reduce the reliability of business process greatly.Due to absent of transaction support,most existing replacement mechanisms are of poor adaptabilities.Therefore,the atomicity and the consistency of the transactional service can not be well assured during the system implementation process,and the correctness,the real-time performance and the efficiency of the replacement process can not be guaranteed either.This paper takes the "transaction support" as the core and proposes an active and opportunistic transactional composite service replacement algorithm,which fully takes into account the multiple relationships among Web services and the transactional characteristics of Web services.In this paper,the authors first present a mechanism to obtain the transactional granularity and a method to identify the cascading compensation range,then,propose a transactional replacement cost/benefit QoS model,which completes service replacement with the least cost by integrating transactional compensation service QoS and service replacement QoS.Further,a novel QoS-driven services replacement algorithm with the transactional compensation support is designed.In order to enhance the real-time performance,the authors introduce the early prediction pattern mining to identify the failed or unavailable services as earlier as possible by adopting a real-time monitoring to the running services.Experimental results show that the proposed model not only guarantees the atomicity and the data consistency of the process business in the replacement,but also improves the reliability and the real-time performance of the system.