Wrth reswm, bydd angen data cadarn a chywir, sy'n gallu cefnogi trefniadau adrodd rheolaidd, i gyd-fynd â'r holl gerrig milltir. Mae'n debygol y bydd angen cyflwyno'r cerrig milltir gam wrth gam a bydd hi'n bosibl i'r rhan fwyaf, os nad pob un ohonynt, fod yn eu lle erbyn 2021.
All milestones will of course need to be supported by robust and accurate data that can support regular reporting. The milestones will likely need to be introduced on a phased basis with the potential for most, if not all, to be in place by 2021.