4.1 time frame

In the text, you suggest using the IVOA vocabulary, which is a very good thing, and then there's a table 7 time scale which is different from 
https://www.ivoa.net/rdf/timescale/2019-03-15/timescale.html
It would be good either to harmonise or, better still, to reference the vocabulary and, if necessary, to extend it.