Stability measurement model for service-oriented systems

Service technology, such as Web service, has been part of the mainstream of software development for some time due to its promising characteristics such as interface-implementation decoupling, reusability, and composability. Like other software, a service has to undergo maintenance during its lifetime to cope with changes in requirements and environment or to handle errors. Unfortunately certain changes of a service, especially service interface changes, can have effects on other parts of the system which use the service. It is therefore useful to determine service stability so that a service designer can determine how well the service-oriented system evolves while preserving the design. This paper proposes a stability measurement model for service-oriented systems. The model is based on logical stability of a Web service which is measured by the degree of unchanged elements of the service interface during its evolution from one version to another. The paper considers stability between any pair of service and system versions as well as the overall stability of the service and system which involve several parallel versions. The knowledge of service stability can help the service designer during maintenance of the serviceoriented system since the new service version should be designed to preserve stability and cause as minimal impacts as possible. The service designer can also observe how stable the services and the whole system are over their lifetime when considering service reuse or planning service maintenance cost and effort.