CROWN: A Service Grid Middleware for e-Science - Grid Computing: Infrastructure, Service, and Applications - page 14

lightweight embedded runtime. However, these basic functions are
not enough to satisfy the requirements for a service container in a real
grid environment.
RLDS contains three components:

1. Domains: Nodes are organized into different domains according
to their subordination or resource catalogs. An RLDS is deployed
in each domain as the center of grid information management.
Domains may contain several subdomains such that all RLDSs
come up with a tree-like topology.

2. Regions: For l exibility, the concept of a “region” is introduced to
coordinate different domain trees. A region switch is deployed in
each region such that l exible topologies and information sharing
mechanisms can be applied among regions.

3. Gateways: To connect with other grid systems, we deploy several
gateways on the edge of the CROWN system.

1.3.3 S-Club and RCT

CROWN employs a service club mechanism, called S-Club, for efi cient
resource organization and service discovery. S-Club is used to build an
efi cient overlay over the existing GIS (grid information service) mesh net-
work [7-9]. In such an overlay, GISs provide the same types of services
organized into a service club. An example of such a club overlay is shown
in Figure 1.6, where nodes C, D, E, and G form a club. A search request
could be forwarded to the corresponding club i rst such that searching the

Has service of type T
G

C

D

Has service of type T

E

Has service of type T

Has service of type T

FIGURE 1.6 An example of service club.