G: General

G1: What is a VOTable and what are the benefits of using it?

The VOTable format is an XML standard for the interchange of data represented as a set of tables. VOTable is designed as a flexible storage and exchange format for tabular data, with particular emphasis on astronomical tables. For more information see the VOTable Format Definition.

The VOTable format has been designed to resemble that of the FITS binary tables but overcoming the limitations present in FITS. One can convert tables between VOTable format and FITS, but the metadata describing the table and its columns is lost in the process.

QB: Query Builder

QB1: You enter what appears to be a valid query in the ADQL/S pane of the query builder and when going back to the TREE view you get a parsing error (see e.g. Bug-2025)

Column names which are reserved words such as "dec" or which begin with a non-alphabetical character should be enclosed in inverted commas e.g. SELECT * FROM table AS t WHERE t."dec" > 10.0 AND t."2mass" < 17

NAW: 20 Oct 2006

QB2: What is the syntax used in the query builder?

The sysntax for the (Dec 2006) ADQLv1 is available

NAW: 1 Dec 2006

DH: Data Handling

DH1: Your data file is large and written in ascii VOTable format. It takes for ever to load into for instance TopCat.

To improve performance the best solution is to convert from ascii to binary format. One technique is to download the file from MySpace to your desktop. Then use the STILTS tcopy utility to convert from votable to fits e.g.

java -jar stilts.jar -disk tcopy <filename>.vot <filename>.fits

NAW: 1 Dec 2006

DH2: You have a VOTable which you would like to import directly into IDL without converting it to another format first.

VOTables can be imported directly into IDL using the readvot.pro procedure which is available from the VO IDL Software Libraries web page. One must download the whole VOlib package and follow the instructions in the README file to install the libraries. One correctly installed, it is simply a case of typing the following at the command line.

readvot, '<filename>', data

where <filename> should be replaced by the name of the VOTable and data is the IDL structure that the data will be imported to.

DW: 27 Mar 2007