ImplementationCase: Find VObsServices giving access to a specifc ScienceResource

Motivation

• To use the ScienceResource in an experiment.
• To find alternative endpoints for using the resource.

Story

A user Agent has instructions to identify possible VObsServices for use in a job step. Agent may be a web portal, in which case the instructions come from a web form, or may be a semi-autonomous agent, in which case, the instructions are part of Agent's orginal script. In each case, the instructions state the IVORN of the ScienceResource to which the VObsServices must given access.

Agent translates the instructions into a query document suited to the standard IVOA interface for resource registries.

Agent sends the query to a Resource Registry. It doesn't matter which one because all IVOA registries harvest all IVOA resources.

Registry executes the query and sends back to Agent a list of matching resources.

Discussion

The metadata returned by Registry to Portal are a list of VObsService, a sub-class of VOResource.

The list may have more than one entry if:

• there are copies of the ScienceResource with the same interface at different addresses; e.g. mirrors of a data set;
• there are different interfaces to the ScienceResource; e.g. a cone-search interface and a Sky Node interface.

Thus, the return from the query has to carry enough metadata to inform a selection or to show that a revised query is needed. The metadata must be intelligible both to a uman user (if Agent sends them on to a UI) or to a programme (if Agent itself is to choose a service).

-- GuyRixon - 19 May 2004