bnf

[Danielle et jean Thierry-Mieg]

i rather like the proposal


FOO f
tag a b
tag c d tag3 e

where tag3 is in a submodel, then

  ee = ff.tag[2][tag3]

i have to get used to it, but i think it is natural

and if i want what is right of c i would have to do it
as a constraint WHERE tag[1]=c, i suppose ?