Francois Ochsenbein (CDS, Strasbourg), Miguel Albrecht (ESO-Garching), Allan Brighton (ESO-Garching), Pierre Fernique (CDS, Strasbourg), Damien Guillaume (Queen Univ., Belfast), Robert Hanisch (STScI, Baltimore), Andreas Wicenec (ESO-Garching)
XML - the Extensible Markup Language - is a developing standard in which the description of the data (the metadata) is included with the actual data in a single electronic document. XML is very general and is being adopted for use in many disciplines. By using XML for the description of information, one achieves independence from the application used to manipulate it, e.g. whether the data are just being displayed by web browsers - or used within a scientific reduction pipeline. In order to make such documents available to a large range of applications, common XML Document Type Definition (DTD's) need to be agreed upon.
The usage of XML in the context of astronomical data was already investigated by E. Shaya (NASA GSFC/ADC) and D. Guillaume (U. Belfast). The present paper focuses on the use of XML for accessing and understanding tabular data, particularly for the case of handling the responses from queries to on-line catalog services. If such responses are encoded in XML using agreed upon tags and attributes, it is possible to both display the data in clearly formatted tables and use the data in other applications (such as generating graphical overlays of object positions on survey images). XML-encoded tables can also provide the basis for the next generation of data discovery and integration tools (Astrobrowse, ISAIA).
The detailed definitions of XML tags and attributes that are currently being defined, including examples and a working DTD, are described at http://vizier.u-strasbg.fr/doc/astroxml.htx. The definitions have been developed with compatibility with FITS standards as a goal. The proposed XML DTD will be discussed at the JSky BOF.