Variance, like Vega, draws a ton from Wilkinson's "Grammar of Graphics". In particular I wanted something like Hadley Wickham's ggplot2 R library, but on the web.

I toyed with the idea of an explicit data format that could be generated by different tools (I talked about this at the 2012 Clojure/conj https://www.youtube.com/watch?v=xyGggdg31mc). Conceptually that route is cleaner.

However, the reality is that any such scheme requires "escape hatches" to drop into the target representation (be it HTML/CSS, Canvas, &c.). We decided it would be best to embrace a single target, HTML+CSS, rather than try to build an abstraction targeting multiple final rendering systems.