ImplementationCase: results of query stored as VOSpace branch

Motivation

• Visualize results of queries.
• Make query results persistent.
• Build up tree of pointers to data sets.

Story 1

An Agent has made a query that returns only metadata. The query results contain a list of pointers to data sets that can be downloaded but not the data themselves. SIAP and SSAP queries work this way.

Agent picks a directory in VOSpace to store these results. For each entry in the list of results, Agent executes IcCreateNodesInVOSpace, story 1 or 2, adding one leaf node to the directory. Agent edits the metadata of this node, setting it to point at the data set in the query results.

Story 2

As story 1, but Agent converts the output of the query into VOSpaceMarkupLanguage (VOSML), thus expressing the VOSpace nodes for the external data-sets in on XML fragment. Agent then executes IcCreateNodesInVOSpace story 3.

Story 3

As story 1 or story 2, but the query is repeated on many different data archives and the results need to be collected together. Agent makes a sub-directory in VOSpace for each data source and puts the results from the source in that directory.

Story 4

As story 3, but the results for individual archives have some structure. E.g., an archive may return results in different filter passbands grouped by target. Agent copies the hierarchical structure to VOSpace, creating directories as necessary.

Discussion

SIAP and SSAP have an application-specific output format based on VOTable. Results in this format can be stored, but need SIAP-aware software to parse them. Therefore, it's hard to include the SIAP results in a workflow. If the results are made to appear in VOSpace (as links to data-sets outside VOSpace), then they are more accessible to software.

The tree presentation of a group of data-sets may be better for human users. The use of a data tree is an important feature in the AVO version of Aladin. A similar feature was shown in a CASU demo at ADASS 2001.

If VOSML emerges as a usable feature from the VOSpace work in IVOA, then it could be used as the output format of SIAP-like services. This would satisfy the need for hierarchical structure debated recently in the VOTable working-group of IVOA.

-- GuyRixon - 30 Jun 2004