QuickStudy: Open Grid Services Architecture

Computerworld - Definition:
Open Grid Services Architecture (OGSA) is a set of standards that extends Web services and service-oriented architecture to the grid computing environment. OGSA definitions and criteria describe how information is shared and distributed among the components of large, heterogeneous grid systems; they apply to hardware, platforms and software.

Grid computing has intrigued the IT world for years. The notion of harnessing the processing power of multiple computers  whether within an organization, supplied by volunteers or provided as a broadband, metered computing utility  is attractive and compelling, but implementing it has proved somewhat difficult. One of the more recent developments advancing this cause, OGSA extends the idea of Web services to the universe of grid computing and thereby extends and refines the concept of service-oriented architecture.

To create workable grid services, developers have had to address several important issues: how to establish identity and negotiate authentication, how to express and negotiate policy, how to find out what services are available, how to negotiate and monitor service-level agreements, how to organize and manage collections of services to deliver reliable and scalable services, and how to integrate data resources into computations.

OGSA is based primarily on the technologies of Web Service Description Language (WSDL) and Simple Object Access Protocol (SOAP), an XML-based protocol for passing messages between systems over the Internet. It is service- oriented because it works as a series of loosely coupled, interacting services that use industry-accepted Web services standards.

For a Web service to be considered a grid service, clients must be able to easily discover, update, modify and delete information about the service and its functionality and relevant data; define how the service evolves; and ensure ongoing compatibility with other services.

Origins

OGSA began with work in the late 1990s at Argonne National Laboratory, IBM, the University of Chicago and other institutions. Today, OGSA development activities are under the direction of the Open Grid Forum (www.ogf.org). This community, representing more than 400 organizations worldwide, was formed by the 2006 merger of the Global Grid Forum and the Enterprise Grid Alliance.

What OGSA Does

OGSA builds on concepts and technologies from both the grid and Web services communities, defining a uniform vocabulary and grammar for grid services. OGSA represents almost everything you can do as an instance of a grid service  that is, a transient Web service that can be located within the grid and combined dynamically with other services to form larger systems and applications. The transience is what makes a grid service different from a Web service. Transience means the services can be activated and deactivated in a timely manner without destroying the data required for many operations.