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The recent explosion of commercial and scientific interest in the Grid makes it timely to revisit the question: What is the Grid, anyway? I propose here a three-point checklist for determining whether a system is a Grid. I also discuss the critical role that standards must play in defining the Grid.

The key concept is the ability to negotiate resource-sharing arrangements among a set of participating parties (providers and consumers) and then to use the resulting resource pool for some purpose. We noted:

"The sharing that we are concerned with is not primarily file exchange but rather direct access to computers, software, data, and other resources, as is required by a range of collaborative problem solving and resource-brokering strategies emerging in industry, science, and engineering. This sharing is, necessarily, highly controlled, with resource providers and consumers defining clearly and carefully just what is shared, who is allowed to share, and the conditions under which sharing occurs. A set of individuals and/or institutions defined by such sharing rules form what we call a virtual organization."

We also spoke to the



ance of standard protocols as a means of enabling interoperability and common infrastructure.

A Grid Checklist

I suggest that the essence of the definitions above can be captured in a simple checklist, according to which a Grid is a system that:

1) ... coordinates resources that are not subject to centralized control ...

2) ... using standard, open, general-purpose protocols and interfaces ...

3) ... to deliver nontrivial qualities of service.

The Grid: The Need for InterGrid Protocols

My checklist speaks to what it means to be "a Grid," yet the title of this article asks what is "the Grid." This is an important distinction. The Grid vision requires protocols (and interfaces and policies) that are not only open and general-purpose but also standard. It is standards that allow us to establish resource-sharing arrangements dynamically with any interested party and thus to create something more than a plethora of balkanized, incompatible, non-interoperable distributed systems. Standards are also important as a means of enabling general-purpose services and tools.

In my view, the definition of standard "InterGrid" protocols is the single most critical problem facing the Grid community today.

Both open source and commercial products will interoperate effectively in this heterogeneous, multi-vendor Grid world, thus providing the pervasive infrastructure that will enable successful Grid applications.

- "What is the Grid? A Three Point Checklist," Ian Foster http://www-fp.mcs.anl.gov/~foster/, Argonne National Laboratory & University of Chicago, Global Grid Forum http://www.ggf.org, Understanding Grids http://www.ggf.org/ggf_grid_understand.htm, July 20, 2002

Directory: http://www.larryblakeley.com/Articles/clusters_grids/

File Name: ian_foster20020720.pdf

Post Date: June 4, 2005 at 12:55 PM CDT; 1755 GMT