Analysis of User driven Availability and Resource level Availability for a Composite Web Service

摘要

Composition of Web services plays an important role in defining a new service in the business environment. When defining a new web service, it is very important to preserve the quality attributes as promised in Service Level Agreement (SLA). High Availability is considered as one of the most significant quality attribute in the SLA. Since the Composite web service is a combination of multiple autonomous services, it is very challenging to assure that the quality attributes will be met as per the Service Level Agreement (SLA). For a composite web service, the workflow for each service request is dynamic in nature. To guarantee the availability of Composite web service as per SLA, appropriate modeling technique is essential to compute the availability. In this paper, model based approaches to compute the availability of composite web service from the perspective of users and from the perspective of resources is proposed. Conditional Probability Tree and Markov model are employed to compute user driven availability and resource level availability respectively. The experimentation and the results of validation are very promising and provide a way to use our technique for Composite web service for proper implementation of SLA.