How Everything Relates

If you have been following these pages sequentially then you will have been introduced to the main OGSA-DAI components: data services, data service resources, data service resource accessors and data resources. This page summarises and illustrate the relationships between all of these.

Data Services, Data Service Resources and Data Resources

The following diagram shows a typical deployment scenario.

• A data service can expose zero or more data service resources.
• The data service and its data service resources are resident on the same server.
• A data service resource exposes one data resource.
• The data resource need not be resident on the same server as the data service resource.
• A data resource accessor manages interactions with the data resource on behalf of the data service resource.
• A data service resource has an associated set of configuration files. These specify the activities it supports, session information and the class name of its data resource accessor.
• A data service resource accessor has an associated set of configuration files which specify information about the data resource.

This is the typical use case where a data service resource is deployed to expose a relational, XML or files data resource or, in other words, the data service resource is configured to use one of a JDBC, XMLDB or files data resource accessor.

Factory Data Service Resources

The following diagram shows what happens when a data service resource that is configured to use a demo factory data resource accessor is deployed.

• A data service resource configured to use a demo factory data resource accessor has been deployed (that is the Demo Factory Data Service Resource in the diagram, details are ommited for clarity).
• The data service resource has a set of configuration files which specifies the activities it supports, session information and the class name of the demo factory data resource accessor.
• The demo factory data resource accessor (not shown in the diagram) has a set of configuration files for the data service resources it can create which specify the information on the supported activities, sessions and the data resource accessor class name for that data resource.

The following diagram shows the state after the data service resource has received a request to create a new data service resource.

• A new data service resource, the Demo Instance Data Service Resource on the diagram, has been deployed which is configured to use a demo instance data resource accessor (not show in the diagram, as before details are ommited for clarity).
• The new data service resource has a set of configuration files which specifies the activities it supports, session information and the class name of the demo instance data resource accessor.
• The demo instance data resource accessor has a configuration file which is a simple file containing some text which the activities supported by the new data service resource can access (to demonstrate that this all works!).