Measuring Availability of Mobile Web Service

--Adapting present Web services to the mobile environment has raised new Quality of Service (QoS) challenges for both service provider and requester. In a mobile Web services (MWS) scenario, a successful service invocation will depend on (1) service application (2) condition of mobile network and (3) capabilities of mobile device. Hence, from a client perspective, the availability of a service will depend on all three factors. This paper presents an Availability Checking Model (ACM), to determine the availability status of MWS by processing and referring to end-to-end service QoS parameters. This model introduces availability metrics to quantify service availability checking points. These metrics are represented by a XML schema and published as extension to WSDL. We also discuss mechanisms to aggregate server-side, mobile network and client device metrics to calculate the overall availability information. By knowing the end-to-end availability of a service, mobile client may use that information to make necessary decisions such as to proceed with invocation, to look for alternative service, to retry after predefined time or to stop entirely. Besides, this “check before subscribe” approach will help mobile user to save cost as it prevent unnecessary message transactions. For a service provider, this will improve its overall QoS and can be useful reference for managing Service Level Agreement (SLA). Keywords---Availability, Mobile, QoS, Web Services, SOA