SIMBAD is, in the first place, a database of identifications, aliases and names of astronomical objects: in principle any name found in the literature - provided it is given as a syntactically correct character string - can be submitted to SIMBAD in order to retrieve basic information known for this object, as well as pointers to complementary data and bibliography. This implies a continuous careful cross-identification of objects from catalogues, lists, and journal articles. This ability to gather together any sort of published observational data related to stars or galaxies is the first key feature of SIMBAD.
Another unique feature is the complete and up-to-date bibliographic survey of the astronomical literature: objects are associated with the references of all papers in which they are mentioned, independently of the aliases used to name the object.
In addition, the Dictionary of Nomenclature (Sect. 8) is an essential tool for managing the very complex nomenclature of objects found in the literature, and for matching naming variations with those adopted or simply accepted by SIMBAD. It also includes hints for helping to solve ambiguities, according to the type of object, or to the format. This is complemented by the sesame module within SIMBAD, for the management of possible variations in the naming of astronomical objects.
The database management system of SIMBAD (Sect. 4) has been developed in-house at CDS, using the concepts of object-oriented programming.
SIMBAD is kept up-to-date (Sect. 7) on a daily basis, as the result of the collaboration of CDS with bibliographers in Institut d'Astrophysique de Paris and the Paris and Bordeaux observatories.
The statistical contents of the database (Sect. 3) can be summarized in a few figures as follows (the figures quoted are statistics of November 1999):
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