13.2.1 Epoch propagation functions

Since one of the main features of Gaia DR2 is the inclusion of proper motions for nearly all sources of the Gaia catalogue, epoch propagation functions have been added to the ADQL syntax and have been implemented in the Gaia Archive. These functions, which follow the implementation defined in ESA (1997), have also been extended to allow integration into cone-search and crossmatch operations using ADQL. See https://www.cosmos.esa.int/web/gaia-users/archive/writing-queries/#EpochPropagationFlag for details.