The VO has a “registry"that keeps an inventory of the services and data kept within the VO. TAP services communicate basically what’s in TAP_SCHEMA to the registry.
There are a few ways to search the registry. In TOPCAT we already used the key word search in the TAP service window. Another way to search the registry is WIRR. With the Web Interface to the Relational Registry (WIRR) you can search the VO registry in a more elaborate way. WIRR is not limited to search TAP services only, but also services using other VO protocols like SIAP or SCS. For now our use case will be to find tables talking about quasars having a column containing redshifts:
In the query field on top select"Text Fields"-"match"-"quasar"
then click"+"and in the new appearing row select "Service Type"-"is"-"TAP(SQL)",
again click"+"and in the new row select "Column UCD"-"like"-"redshift"
Note that WIRR offers help what the queries mean if you click on"Info"at the end of each row."
Find out the UCDs for redshifts and proper motion.