As one of the main features of the Gaia DR2 is the inclusion of proper motions for all the sources
of the Gaia catalogue, epoch propagation functions have been added to ADQL syntax and implemented
into the Gaia Archive database.
These functions, following the implementation defined into ESA 1997 SP-1200 reference document
”The Hipparcos and Tycho Catalogues”, has been also extended to allow easier integration into
cone search and crossmatch operations using ADQL.