Master Thesis - ICS

Computer Science Department
Antonis Misargopoulos
repair cannot remain manual tasks. These requirements resemble the self-organizing and
healing properties of biological systems, and have been termed “autonomic” after the
autonomic nervous system. According to the definition in [12], an autonomic system has
the following properties:
• needs detailed knowledge of its components and status;
• must configure and reconfigure itself dynamically;
• seeks to optimize its behavior to achieve its goal ;
• is able to recover from malfunction;
• protects itself against attack;
• is aware of its environment;
• implements open standards; and
• makes optimized use of resources.
The third generation Grid systems now under development are beginning to exhibit many
of these features. In the following section we describe the nature of a Grid with respect to
architectural components and services.
2.4 The Nature of the Grid Architecture
In this section, we identify requirements for general classes of components in the Grid
architecture. The result is an extensible, open architectural structure within which
solutions to key VO requirements can be placed and which is organized in layers, as
shown in figure 2.1. In specifying the various layers of the Grid architecture, we follow
the principles of the “hourglass model” as presented in [1]. The narrow neck of the
hourglass defines a small set of core abstractions and protocols e.g., TCP and HTTP on
the Internet, onto which many different high-level behaviors can be mapped (the top of
the hourglass), and which themselves can be mapped onto many different underlying
technologies (the base of the hourglass). By definition, the number of protocols defined
at the neck must be small. The neck of the hourglass consists of Resource and
Connectivity protocols, which facilitate the sharing of individual resources. Protocols at
these layers are designed so that they can be implemented on top of a diverse range of
resource types, defined at the Fabric layer, and can in turn be used to construct a wide
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