An astronomical information service on the World-Wide Web has been made publicly available at CDS, Strasbourg, since December 1993. It provides access to the following documents and services:
The current average consultation rate is about 1,600 documents per day. The most popular services are the Catalogue service (more than 1,200 catalogs and tables, and 5 Gigabytes of data are available on-line), the Abstract service (original aauthor abstracts are made available 4 weeks in advance of publication, through an agreement with the Editors), and the Star*s Family (refer to Heck et al. in these proceedings).
An important feature provided by the World-Wide Web is the ability of creating links between different services: this is true at the level of portal or descriptive pages where hyperlinks allow, for instance, to inform SIMBAD users about the catalog or abstract services. But this is even more crucial at the level of data items: as an example, when a user retrieves the abstract of a paper for which data tables are available, the abstract carries an anchor pointing to these tables which can be browsed after a simple mouse click.
For the SIMBAD database a specific client application for X-Window, running on Unix stations, is currently preferred both for technical (WWW is stateless and therefore not well suited for interactive queries) and political reasons (SIMBAD is a charged service, while the WWW currently hosts mostly free services).