The OGSA Model: Dynamic Service Creation And Management

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 Dynamic Service Creation: The OGSA model can dynamically create and manage new service instances and also can necessitate the existence of service creation services. The OGSA model defines a standard interface (Factory) and semantics which a service creation service must provide [1].
 Lifetime Management: Any distributed system is supposed to deal with any number of failures. Especially in a system which involves transient, stateful service instances, there should be an option available to reclaim the lost services and also for recovering the state associated with the failed operation [1].
 Notification: The collection of distributed services should be able to alert each other asynchronously when any change occurs to their current state.
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4.3 Service Groups and Discovery Services:
A service group can be defined as a collection of entries where each entry represents a grid service implementing the ServieGroupEntry interface. Each and every service will need some means for discovering services with particular properties. The ServiceGroup interface also extends the Grid service interface and there is a ServiceGroupEntry in each service of the group. There is ServiceLocator in each if these entries which contain the information related to referred-to service and also information about that service.
4.4 Choreography, Orchestration and Workflow:
OGSA provides a rich set of behaviours along with associated operations and attributes for business process management. Some of them are Job Flow definitions, resource assignment to Grid flow instance, scheduling and execution of grid flows and associated grid services, common context and metadata for grid flows, managing, monitoring and failure handling for grid flows.
NWEN406 Essay #1
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This service will provide a set of terms which indicates the time duration, resource requirement specification and authorized user/project agreement terms.
4.18 Data Access Agreement Service:
The Data Access agreement service allows the end users or a job agreement service to stage application or required data.
4.19 Open Grid Services Infrastructure (OGSI):
OGSA has been constructed on the fundamental mechanisms of OGSI. These mechanisms are used to address issues relating to the creation, naming, management, and exchange of information among entities called grid services. OGSI also introduces standard factory and registration interfaces. The key OGSI features are Grid Service descriptions and instances, Service state, metadata and introspection, naming and name resolution, fault model, life cycle and service groups.
4.20 Common Management Model
The Common management model defines the base behavioural model for all resource and resource managers in the grid management infrastructure.

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