A Fault Tolerant Mechanism for Composition of Web Services Using Subset Replacement

Abstract: Businesses offer complex services to the users, which can’t be provided by a single Web Service. A Composite Web Service provides more complicated function, by composing multiple Web services. A composite service is more susceptible to failure than an atomic service. During the execution of a Composite Web Service, if one Component Service fails or becomes unavailable, the whole Composite Web Service fails. A middle agent (broker) simplifies the interaction between service providers and service requester and fulfills the user's need. The broker composes a desired value-added service and orchestrates the execution of Web Services. A replacement policy has been proposed in this paper that replaces the subset of Web Services that contains failed Web Service with another equivalent subset. During the execution, if a failure occurs, subsets containing failed Web Service are identified. Subsequently the subsets equivalent to failed one are identified. These equivalent subsets are ranked as per the policy and the best subset is selected. The old subset is replaced with the new equivalent subset in the Composite Web Service.

Keywords: Web Services, Composition, Subset Replacement, Equivalent Services.