Information on Service 'UCL DaCHS server TAP service'

The UCL DaCHS server's TAP end point. The Table Access Protocol (TAP) lets you execute queries against our database tables, inspect various metadata, and upload your own data. It is thus the VO's premier way to access public data holdings. Tables exposed through this endpoint include: columns, groups, key_columns, keys, schemas, tables from the tap_schema schema, epn_core from the jasmin schema, emptyobscore, obscore from the ivoa schema, epn_core from the mdisc schema.

For a list of all services and tables belonging to this service's resource, see Information on resource '__system__/tap'

Service Documentation

This service speaks TAP, a protocol designed to allow the exchange of queries and data between clients (that's normally something running on your computer) and servers (e.g., us).

You will want to use some sort of client to query TAP services; examples for those include:

You can, in a pinch, use our service in an XML-enabled browser, too. Under Overview, look for the bullet point on tap and follow the link to "this service". Then, click on "New job..." in the job list, enter your query, click "Set query", then "Execute query". Reload the page you are redirected to now and then to see when your job is finished, then retrieve the result.

The queries this service executes are written an a dialect of SQL called ADQL. You need to learn it to use this service. See our ADQL tutorial. Also do not miss the local examples.

By the way, for quick ad-hoc queries from within a browser, our ADQL form service may be more convenient than TAP.

Also see the table metadata of the tables exposed here.

Issues

For information on our ADQL implementation, see the ADQL service info.

While columns with xtype adql:POINT are correctly ingested into the database, adql:REGION columns are left alone (i.e., they are strings in the database). The reason for this behaviour is that in order to infer a column type, one would have to inspect the entire table up front.

If multiple output columns in a query would end up having the same name, in the output VOTable they are disambiguated by appending underscores. This is in violation of the specification, but since fixing it would require rather intrusive changes into our software and it is not clear why one should want to use names when they are not unique to begin with, this will probably not be fixed.

Overview

You can access this service using:

This service is published as follows:

local means it is listed on our front page, ivo_managed means it has a record in the VO registry.

VOResource XML (that's something exclusively for VO nerds)