Resources In The Grid Environment And Design Of Information Services

In the latest years, the Grid community has undertaken a development effort to align Grid technologies with Web Services. The Open Grid Services Architecture (OGSA) defines Grid Services as an extension of Web Services and lets developers integrate services and resources across distributed, heterogeneous, dynamic environments and communities . Web Services define a technique for describing software components to be accessed, methods for accessing these components, and discovery methods that enable the identification of relevant service providers. Web Services and OGSA aim at interoperability between loosely coupled services independently from implementation, location or platform. The OGSA effort aims to define a common resource model that is an abstract representation of both real resources, such as processors, processes, disks, file systems, and logical resources. It provides some common operations and supports multiple underlying resource models representing resources as service instances. The OGSA model provides an opportunity to integrate P2P models in Grid environments since it offers an open cooperation model that allows Grid entities to be composed in a decentralized way.A core Grid functionality that could be effectively redesigned using the P2P model is resource information service. Resource information service is a key issue in Grid environments, since applications are usually constructed by composing hardware and software resources that need to be discovered and selected. In the OGSA framework each resource is represented as a Grid Service, therefore resource information service mainly deals with the problem of providing, registering and querying information about useful Grid Services. In Globus Toolkit 3 (GT3) - the current implementation of the OGSA - information about resources is provided by Index Services. An Index Service is a Grid Service that holds information (called Service Data) about a set of Grid Services registered to it. A primary function of the Index Service is to provide an interface for querying aggregate views of Service Data collected from registered services. There is typically one Index Service per Virtual Organization (VO). When a VO consists of multiple large sites, very often each site runs its own Index Service that indexes the various resources available at that site. Then each of those Index Services is included in the VO's Index Service.This paper proposes an architecture for resource information service system that adopts a P2P approach to extend the model of the GT3 information service. In particular, a P2P Layer of specialized Grid Services is defined to support discovery queries on Index Services of multiple VOs in a P2P fashion. The paper also design a set of software components of Grid Resource Information System: such as the provider component, registering component ,service data indexed component and interfaces for client application . At last, the paper compare the P-RIS with other information service systems: such as UDDI, MDS of Gloubs, and P2P information service .