N. Looker “Dependability Assessment of Services ,” presented at Seventh SOSoRNet Workshop on Dependable, Dynamic Distributed Services and Systems, 6th November 2007, Woodhouse Rooms, University House, University of Leeds.
Abstract: Web Services are a heavily used middleware in eCommerce and also make a major contribution to Grid computing. Given the prominence of this technology it is vital that methods are developed to ensure that dependable services and middleware products are deployed.
Dependability is a discipline that provides an assessment of how much trust can be placed on a service to deliver its specified function. Systems need not be fault free but should deliver their required functionality when required. This is because it is virtually impossible to engineer a system that can be guaranteed to be fault free; so dependability assumes that faults exist in a system but mechanisms exist to either eliminate them or tolerate their presence. In either case a dependable system will perform its intended function.
Validation and verification techniques attempt to determine that a system contains no faults, which is an important discipline and increases the overall reliability of a system, but is difficult to achieve with current techniques. Dependability is a more realistic approach since it measures the reliance that can be placed upon a system rather than validating it against its specification and includes methods that increase this.