4. Macro Tree Transducers
Combine  Top-Down Tr Tr. and CFT grammars!
Def.:   A  Macro Tr. Tr. is   (Q, S, D, q0, R)
    Q               ranked alphabet of states
    S, D           input / output ranked alphabets 
    q0 2 Q(0)    initial state
q
s
x1
xk
…
à
hq’,xii
Rules in R:
hq’’,xji
( y1, …, ym )