scheme :: DTCONSTR:sch 7
DTConstrInd{ F1() -> non empty DTConstrStr , P1[ set ] } :
for t being DecoratedTree of the carrier of F1() st t in TS F1() holds
P1[t]
provided
A1: for s being Symbol of F1() st s in Terminals F1() holds
P1[ root-tree s] and
A2: for nt being Symbol of F1()
for ts being FinSequence of TS F1() st nt ==> roots ts & ( for t being DecoratedTree of the carrier of F1() st t in rng ts holds
P1[t] ) holds
P1[nt -tree ts]