+ 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.