Variability Analysis: Detection and Classification
  Gaia mission will offer an exceptional opportunity to perform variability studies. The data homogeneity, its optimised photometric systems, composed of 11 medium and 4-5 broad bands, the high photometric precision in G band of one milli-mag for V=13-15, the radial velocity measurements and the exquisite astrometric precision for one billion stars will permit a detailed description of variable objects like stars, quasars and asteroids.   However the time sampling and the total number of measurements change from one object to an other because of the satellite scanning law. The data analysis is a challenge because of the huge amount of data, the complexity of the observed objects and the peculiarities of the satellite, and needs a thorough preparation.   Experience can be gained by the study of past and present survey analysis and results and Gaia should be put in perspective with the future large scale surveys, like Pan-STARRS or LSST.   We present the activities of the Variable Star Working Group and a general plan to digest this unprecedented data set, focusing here on the photometry. 
Laurent Eyer (Observatoire de Geneve)