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3. The World Wide Web server

The real new effort done is the development of a server on the World Wide Web, which permits an easy data retrieval in various ways. The present interface has been designed to retrieve data for small numbers of stars or prepare samples based on magnitudes or colour indices. The possibility to enter the database with a list (file) of stellar identifications will be investigated. For intensive use of the database, i.e. a large sample of predefined stars, it is still better to contact the authors. There are basically three forms to query (1) the Master Index, (2) each photometric system directly, and (3) the bibliographic reference files.

3.1. The Master Index

The query of the Master Index is aimed at displaying the existing information for one or several stars. It uses the power of hypertext to link the displayed information with CGI scripts that query the database and display further information. The query of the Master Index is possible with either a basic star identification, or co-ordinates. The output page presents the number of available data and a simple click on the link displays the real data in the selected photometric system. The query by coordinates (equinox 1950 or 2000) will display the same information for the stars falling in the area defined by the central co-ordinates and the given limits in right ascension and declination.

3.2. The photometric files

When the observations for one or several stars are desired in a specific system, the second form offers a direct access to each of the 78 photometric systems. Each photometric catalogue may be queried by star identification or co-ordinates. Selection on the photometric indices and parameters can also be made.

3.3. The references

Access to the references make it possible to look for the papers published by an author or to search for some words in the titles of the papers. The link added to the output permits to display the whole dataset corresponding to the publication selected. This facility allows to easily get on-line data from 2526 papers published from 1953 to 1995. The stellar identifications are generally decoded and displayed with the usual acronyms, although many small lists do not have any acronyms and the code numbers are given. The Web site also contains the description of the code numbering system where all definitions and references can be found. A cross-link has been established with the ADS Abstract Service (Eichorn et al. 1996). We have added in our database the bibliographical code used by the ADS services and one can thus directly query the Abstract Service from our pages. Conversely, when papers are obtained from a query of the ADS, data can be directly obtained with the datalink provided, which is connected to our database.

3.4. The Web site

In addition to the form to query the database, the Web site offers varied information, as for example, a technical description of the photometric systems, or selected references to calibration papers.

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