Optimal Fault Tolerance Strategy Selection for Web Services

Web services are self-contained, self-describing, and loosely-coupled computational components designed to support machine-to-machine interaction by programmatic Web method calls, which allow structured data to be exchanged with remote resource. In the environment of service-oriented computing (Zhang et al, 2007), complex service-oriented systems are usually dynamically and automatically composed by distributed Web service components. Since the Web service components are usually provided by different organizations and may easily become unavailable in the unpredictable Internet environment, it is difficult to build highly reliable service-oriented systems employing distributed Web services. However, reliability is a major issue when applying service-oriented systems to critical domains, such as e-commerce and e-government. There is thus an urgent need for practical reliability enhancement techniques for the service-oriented systems. By tolerating component faults, software fault tolerance is an important approach for building reliable systems and reducing the expensive roll-back operations in the long-running business processes. One approach of software fault tolerance, also known as design diversity, is to employ functionally equivalent yet independently designed program versions for tolerating faults (Lyu, 1995). This used-to-be expensive approach now becomes a viable solution to the fastgrowing service-oriented computing arena, since the distributed Web services with overlapping or equivalent functionalities are usually independently developed by different organizations. These alternative Web services can be obtained from the Internet and employed for the construction of diversity-based fault tolerant service-oriented systems. By fault tolerance techniques, long-running business process roll-backs can be reduced since failures of the components can be tolerated by employing alternative candidates (other Web services). Although a number of fault tolerance strategies have been proposed for establishing reliable traditional systems (Lyu, 1995), in the fast-growing field of service computing, systematic and comprehensive studies on software fault tolerance techniques to transactional Web services are still missing.