[NTG-context] Can someone explain the \startuseMPgraphic interface to me?

[Gerben Wierda]

In details.pdf, I encounter

\startuseMPgraphic{mpos:par:columnset:shade}
	numeric h ;
	for i=1 upto nofmultipars :
	h := bbheight(p) ;
	if multikind[i] = "single" :
	fill multipars[i] topenlarged -.5h

When I encounter that, I wonder:
- where do nofmultipars, p, multikind, and multpars come from?
- what does mpos:par:columnset:shade signify? Just a name? Do the ’:’ have meaning?

G.