Setting up Your TAP_SCHEMA Tables

The TAP specification requires that you maintain in your database a set of tables describing your holdings. Pretty much everything about these tables is fixed:

• They have fixed names (like TABLES and COLUMNS)

• They contain a minimum set of columns with fixed names (like COLUMN_NAME)

• They must reside in a separate DBMS “schema” named TAP_SCHEMA

See the TAP specification (http://www.ivoa.net/documents/TAP/), section 4 for details.

All of this is in aid of data mining; a user can issue a set of canned queries against your database to determine your holdings and they can find columns by their function (e.g., coordinates).

The NExScI TAP service makes use of the TAP_SCHEMA tables to inform the presentation of data. In particular, if you want fine control over the formatting of output, you can add a FORMAT column to the COLUMNS table and populate it with C/Python format strings like “6d” to get six-digit integers or “20s” for twenty-character strings.