14 this index service utilizes the standard ogsi

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14. This index service utilizes the standard OGSI notification mechanisms for subscription, notification, and updating of the service data. 15. A Registry of grid services is a set of available grid services that is maintained in the registry. 16. The registry allows a soft state registration mechanism for services to periodically update the overall services availability. 17. A dynamic data generating and indexing node is another valuable feature of the index service. 18. The index service combines ServiceDataProviderExecution components with ServiceDataAggregator and ServiceGroup components to create a dynamic data generating and indexing node. 19. This capability can be utilized to create hierarchical index services.
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Index Service Information Model 1. The base information data model used by the index service is XML. 2. The service data is an XML construct and both client and service know how to deal with this data model. 3. The index service information model provides the exposure of the service data to the clients and aggregation of service data from heterogeneous grid services. 4. Every grid service has service data associated with it and the purpose of index services is to provide an interface to access, aggregate, generate, and query this data. 5. The OGSI-defined GridService interface exposed by all grid services provide a unique way to access and update the service data. 6. These operations are "findServiceData" and "setServiceData."
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Contd… 7. The constructs that are of importance for index service are: 1. Factory, the creator of a grid service. 2. GSH, the unique instance identifier. These GSHs should be converted to GSR before use. 3. GSR, the reference to a grid service with information that includes portTypes exposed by a service, and how the client can communicate with a service. 8. A service data query mechanism enables a service to be queried for the service data information. 9. Registries are used as a common repository for grid services. 10. These registries allow soft state registration of grid services. 11. The most important aspect of index service is the ability to get notified on service data changes anywhere in the grid system.
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Functional Aspects of Index Service 1. A primary function of index service is to provide an interface to a query on an aggregated view of service data collected from other services. 2. The findServiceData operation of the GridService interface is utilized to exploit this query. 3. The index service engine becomes registered as notification sink to other grid services. 4. These notification-enabled grid services establish the subscriptions for notifications on topics of interest that are related to service data. 5. A notification is sent to the sink on state changes. 6. This is illustrated in Figure 9. These asynchronously sent notification messages (i.e., XML messages) are used to monitor the status of the resource, and the current service state information. This notification process can be considered as a push mechanism.
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