+ Various uses and possibilities for obs_publisher_did

1. How the user will be able to make use of it.

This is not a ObsTAP issue, it is a more generic question: Within the IVOA architecture, how to use a obs_publisher_did? For publications? To find again the data? For programmatic access?

1. Given it is a CLOB field, nobody can actually use it to find the same data again (and access_url is volatile).

The IVOA should seriously think how to consume it.

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The dataset identifier is an existing IVOA and ADS standard. It is already in use in the VO registry and in existing DAL standards such as SSA. Hence, there really should be no confusion over the purpose and use of the field. Its main purpose is to identify a specific dataset and allow for later retrieval or access. The current ObsTAP spec is incorrect in specifying that the publisher DID (or creator DID etc.) cannot be used in a WHERE clause to search for datasets; this is the whole purpose of the attribute (unfortunately this was not caught until the current draft was released so we are taking up the discussion here instead).

In addition to the IVOA documents, here is a reference to the original ADS-IVOA agreement where dataset identifiers were originally defined: http://vo.ads.harvard.edu/dv/

This should help to clarify their intended purpose and usage. -- DougTody 2 March 2011