CLUSTER SCIENCE ARCHIVE (CSA) TABLE ACCESS PROTOCOL (TAP)

 

Cluster Science Archive (CSA) content may be accessed through http requests or via the command line (e.g.wget or Python) using Table Access Protocol (TAP: http://www.ivoa.net/documents/TAP/) which has been specified by the International Virtual Observatory Alliance (IVOA: http://www.ivoa.net) and defines a service protocol for accessing general database table data. This subsystem shares the core system of the standard online CSA graphical user interface, but it is called using scripts, application code, command line tools or just a browser.

TAP+ is the ESAC Space Data Centre (ESDC: http://www.cosmos.esa.int/web/esdc/) extension of the Table Access Protocol.

 

DATA REQUESTS:

TAP data requests have been simplified (or 'wrapped') in a way that makes them very similar to the older CAIO protocol requests. If you worked with the old CAIO system and need to update your code to use TAP, this page explains how to do this quickly. If you are new to this method of accessing the system, all the details are here.

Data retrieval can be handled in three different ways depending on what is wanted and how:

  • A Direct or Synchronous Data request allows the user to download data from the archive that fulfil certain search criteria, up to a total (compressed) limit of 1GB. The files are assembled on our server, and then downloaded as soon as it's ready.

  • An Asynchronous Data Request allows the user to download more data up to a total (compressed) limit of 50GB. The files are assembled on our server and an email will be sent to the user when the package is ready for download. This requires the user to be logged in to an account with a valid email address.

  • A Streaming Data Request allows the user to download just one CEF file but start receiving it immediately. This might be useful for visualisation packages.

  • Header retrieval allows the user to download the metadata headers in XML format of the datasets indicated. NOTE: although this is metadata, headers need a Data Request.

 

METADATA REQUESTS:

Metadata requests using TAP are more complex than they were with the old CAIO system. The metadata information is stored in tables which need to be queried using Astronomical Data Query Language (ADQL: http://www.ivoa.net/documents/ADQL/2.0), which is similar to Structured Query Language (SQL), widely used to query databases.

Metadata requests can be used for information about data:

  • Dataset and File Search allows the user to discover datasets and files that fulfil certain search criteria.

  • Inventory information can be requested for a list of datasets within a time interval.

For example, this interface could be used by an application/script that retrieves a list of datasets through a metadata request, and then issues a data request for each item on that list in order to retrieve the data files.

These pages contain details on how to use the different possible requests offered by the CSA-TAP. Additionally, we provide practical examples on how to access the CSA with, for example, just a browser, using the command line with wget or curl, or using Python, MATLAB or IDL.

Should you have any comment, suggestion or find any problem, please contact us.