User-Perceived Service Availability: A Metric and an Estimation Approach

Web-service-related techniques have become popular to improve system integration and interaction. In distributed and dynamic environment, Web services\´ availability has been regarded as one of the key properties for (critical) service-oriented applications. Quality of Service (QoS), including availability, has been regarded by IEEE as a user-perceived property. However, based on our investigation of monitoring invocation records of real Web services, existing availability metrics, which were proposed in traditional domains, have not addressed the "user-perceived\´\´ characteristics. Based on analyzing the limitations of the existing availability metrics, we propose a status-based user-perceived service availability metric and a corresponding estimation approach. Experiments on monitoring and analyzing the invocation records of real services demonstrate that the new metric and the corresponding estimation approach could lead to a feasible estimation on Web services\´ availability from the user side.