Assessing the Reliability and Cost of Web and Grid Orchestrations ∗

Unreliability is a characteristic feature of web and grid based computation: a call to a web or grid site may or may not succeed. An orchestration manager aims to control web or grid behaviour by constructing dynamic threads which acquire and utilise appropriate resources. For example, in an orchestration, a site may be called and may fail to re-spond after a period of time. Subsequently, the site may be recalled, or an alternative site may be utilised. In this paper approaches to estimating the reliability and cost of complex orchestrations are proposed. It is assumed that information about site reliability can be accessed from empirically ac-quired information.