Ekkehard Wieprecht, Erich Wiezorrek, Helmut Steinle (Max-Planck-Institut für extraterrestrische Physik,Giessenbachstrasse 1, D-85748 Garching, Germany) Bart Vandenbussche (Katholieke Universiteit Leuven, Institut voor Sterrenkunde,Celestijnenlaan 200 B, B-3001 Heverlee, Belgium) Christophe Arviset, Arno M. Plug, Richard Saxton (ISO Science Operations Centre, ESA SSD, Villafranca, 28080Madrid, Spain)
We describe User Defined Functions designed to provide the Post Mission Archive of the Infrared Space Observatory (ISO-PMA) with flexibility for sophisticated queries.
During ISO's operational period (November 1995 to May 1998), its four instruments obtained a wide variety of astronomical observations at infrared wavelengths from 2.4-240 microns. About 25.000 observations will be stored in the ISO post mission archive. This archive will provide on-line access to the data, supporting documentation and software through a WWW interface.
The user interface will be HTML and JAVA based and will issue SQL queries to the database via JCONNECT. The basic interface will allow to select observations defined by standard criteria such as coordinates, source name, observing mode, exposure time, wavelength etc. Users can also select data by engineering, trend and housekeeping parameters.
For flexibility, the ISO-PMA is required to allow a wider set of possible queries which also might include simple data processing on the server side. For example, users might want to select spectra of sources within a certain brightness level at a user-defined wavelength, or photometry in a certain color range. It is not possible, however, to execute any procedure other than SQL procedures within SYBASE Transact-SQL (TSQL) statemenents. Operating system commands may be executed in TSQL, but it is not possible to use any local variables when executing the command.
For the ISO Post Mission Archive, User Defined Functions (UDFs) have been implemented to permit definition of functions on linked and viewable data, or products. This system allow users to write their own functions and to execute a required set of TSQL-queries. UDF functions are implemented with a CGI interface to the PMA HTTP server. They are executed by an automatically generated HTML form depending on the supplied definition of the function.
The UDF functions can be written in several languages, either directly invoking SYBASEs interactive SQL utility isql, or using an API to the interface of the SYBASE server. Languages with an API are, among others : SybPerl, SybTCL, WDB, webSQL, Embedded SQL/C and Embedded SQL/COBOL. Basically any language that is able to invoke a system command can be used to execute isql (sh, Perl, tcl, idl).