<p>The increase of satellite instruments sounding the atmosphere will make it very likely that several instruments simultaneously measure either the same vertical profile or vertical profiles related to nearby geo-locations, and users will consult fused products rather than individual measurements. Therefore, the retrieval products should be optimized for the use in data fusion operations, rather than for the representation of the profile. This change of paradigm raises the question if a more functional representation of the retrieval products exists. New variables for the retrieval products are proposed that have several advantages with respect to the standard retrieval products. These variables, in the linear approximation of the forward model, are independent of the a priori information used in the retrieval, allow to represent the profile with any a priori information and can directly be used to perform the data fusion of a set of measurements. Furthermore, the use of these variables allows to reduce to about one third the stored data volume with respect to the use of standard retrieval products.</p>