Castellano

The Grid's vision, of sharing diverse resources in a flexible, coordinated and secure manner through dynamic formation and disbanding of virtual communities, strongly depends on metadata. Currently, Grid metadata is generated and used in an ad hoc fashion, much of it buried in the Grid middleware's code libraries and database schemas. This arbitrary expression and use of metadata causes chronic dependency on human intervention during the operation of Grid machinery, leading to systems which are brittle when faced with frequent syntactic changes in resource coordination and sharing protocols.

The Semantic Grid is an extension of the Grid in which rich resource metadata is exposed and handled explicitly, and shared and managed via Grid protocols. The layering of an explicit semantic infrastructure over the Grid Infrastructure potentially leads to increased interoperability and greater f lexibility. In recent years, several projects have embraced the Semantic Grid vision. However, the Semantic Grid lacks a Reference Architecture or any kind of systematic framework for designing Semantic Grid components or applications. The Open Grid Service Architecture (OGSA) aims to define a core set of capabilities and behaviours for Grid systems.

In this talk we will describe a Reference Architecture that extends OGSA to support the explicit handling of semantics, and defines the associated knowledge services to support a spectrum of service capabilities. Semantic-OGSA (S-OGSA) [1], guided by six design principles, defines a model, the capabilities and the mechanisms for the Semantic Grid. To motivate this work, and illustrate the use of the proposed Reference Architecture, we use the problem of Virtual Organisation management as a case study. We will conclude by highlighting the commonalities and differences that the proposed architecture has with respect to other Grid frameworks that make an explicit use of semantics and semantic technologies, positioning it with respect to the complementary work on Semantic Web Services.