Grid Service Data Needed for Estimation of Reliability in Scientific Workflow Systems

Abstract

The emerging technologies of grid computing, web services, and service-oriented workflows will enable scientific projects to be conducted on a larger scale than ever before. Scientific workflows are often very dynamic in both structure and persistency, complex, and may involve a lot of interaction, very large data flows, and may change on very short notice. Given modern information technology tools, they can be constructed by combining dispersed network accessible services into virtual organizations. Within a scientific workflow environment, metadata or grid service data is necessary for service consumer application to discover services and for services to publish their properties.

Software reliability engineering within service oriented workflow systems is still a largely unexplored area. Emerging standards such as WS-Reliability and WS-Agreement are not yet practical to function in grid service environment. Therefore, methods of leveraging reliability service data with the existing aggregation mechanisms in Globus Toolkit 3, need explored further exploration.

The Open Grid Service Architecture (OGSA) allows registries of services. Service data information in the registries can be used for soft-state management, keeping track of metadata for service instances created from application factories, and so on. A service aggregation registry subscribes to services produced from a number of factories. Service data is express through a proposed XSD namespace shared vocabulary. Discovery policy is expressed in XPath queries.

This thesis proposes one of the first architectures and implementations of a grid service registry information specifically intended for support of fault tolerance and service replica selection in scientific workflow application domain. The registry uses the Globus Toolkit 3 and is made available as an OGSI compliant grid service.