Sidenote: Has Vega* a specific reference to the "Grammar of Graphics" 2005 book [1]? I used that book in research and remember praying for a real implementation. Looking into SO and an answer appeared in 2014 [2].
[1] https://link.springer.com/book/10.1007/0-387-28695-0
[2] https://stackoverflow.com/questions/4892368/implementations-...