The registration form is closed, although the registration to the workshop is still open. Anyone who wants to participate to the Gaia Challenge 3, please, send an email to gaiachallenge3 at am.ub.es with the following information: Name: Affiliation: E-Mail Address: Arrival date: Departure date: Working group of interest: Can you provide a test problem? If yes, briefly describe: Thank you for your interest, the LOC and the SOC.