OAI as VO Harvesting Interface

[Roy Williams]

> (b) Which catalogues does Vizier have giving radio polarisation?
>
>     select [Catalogs] where Manager/Title~'Vizier' and
>       VOTableColumns/FIELD/@UCD=[some ucd for radio polarization]

Perhaps I could amend this in the light of the draft UCD2 specification that
the steering committee has been preparing.

It is no longer just an exact text match as it was in UCD1, but rather a
matching function, mu(u1, u2) which is between 0 (no match) and 1 (excat
match).

Just as ADQL has a text-based "region" specifier, so it will have a UCD
selection mechanism based on an appropriate mu function. I would replace
your Xpath sketch above with a UCDmatch sketch more like this:

select [Catalogs] where Manager/Title~'Vizier'
and "Mu(VOTableColumns, "phot.radio") > 0.8"
and "Mu(VOTableColumns, "pol") > 0.8"