Measuring the Dependability of Web Services for Use in e-Science Experiments

This paper introduces a dependability assessment tool (WSsDAT) for Web Services monitoring and testing. It allows users to evaluate dependability of Web Services from the point of view of their clients by collecting metadata representing a number of dependability metrics. This Java-based tool can be deployed in diverse geographical locations to monitor and test the behaviour of a selected set of Web Services within preset time intervals. The graphical user interface of the tool provides real-time statistical data describing dependability of the Web Services under monitoring. The tool makes it possible for the users to identify typical patters of dependability-specific behaviour depending on the time of the day, days of the week or the client locations, or collect and analyse service dependability measurements during long periods of time, as well to obtain dependability-related information about current service behaviour. The paper reports a successful series of experiments on using this tool for assessing two BLAST Web Services widely used in the bioinformatics domain. The paper shows how the tool can be employed by e-scientists to help them in making informed choices improving the overall dependability of the ‘in silico’ experiments they are performing using a set of distributed services.