COSIM: The necessary evolution of a cross-identification tool along with data evolution

SIMBAD is a bibliographic added-value database on astronomical objects, where the data on individual objects are cross-identified as far as possible. The data comes exclusively from what has been published by the scientific community. To treat large tables, the work is done semi-automatically with the help of a customized software. Since 2014, we are using a new one, called COSIM (Comparison of Objects for SIMBAD). It meets the new requirements which is a consequence of the evolution of the available astronomical data. It has increased in number, accuracy and diversity. On the basis of the data presented in a published table, COSIM searches for objects that are already known in SIMBAD, by name or by coordinates. A combination of scores based on the available and comparable parameters, like the main object type, coordinates, velocity and magnitudes, suggests whether the candidate is good for cross-identification or not. As soon as the result of the search is clear, indicating that there is either no matching candidate or only one good candidate, COSIM creates the commands necessary for updating the SIMBAD database. The documentalists can act on the method of calculation of each score, according to the nature of the objects in the table. Thus, with COSIM the documentalists manage to obtain a good cross-identification level with a minimum risk of omitted or false cross-identifications in a relatively short time compared to the treated data number.