Example of the building process of a simulated Gaia WDMS spectrum. The initial noiseless infinite-resolution theoretical spectrum (top left panel) is rescaled to an specific distance of 5 pc and downgraded to the Gaia resolution (top right panel). It is then filtered through the BP and RP passbands (bottom left panel). A Gaussian noise with a deviation per wavelength interval proportional to the Poisson noise of the number of electrons in that interval is added and, once defiltered, the final synthetic spectrum (bottom right panel) is obtained. See text for details.