set X = F2();
set G = DTConMSA F2();
A3: for s being Symbol of (DTConMSA F2()) st s in Terminals (DTConMSA F2()) holds
P1[ root-tree s]
proof
let x be Symbol of (DTConMSA F2()); :: thesis: ( x in Terminals (DTConMSA F2()) implies P1[ root-tree x] )
assume x in Terminals (DTConMSA F2()) ; :: thesis: P1[ root-tree x]
then ex s being SortSymbol of F1() ex v being Element of F2() . s st x = [v,s] by Lm3;
hence P1[ root-tree x] by A1; :: thesis: verum
end;
A4: for nt being Symbol of (DTConMSA F2())
for ts being FinSequence of TS (DTConMSA F2()) st nt ==> roots ts & ( for t being DecoratedTree of st t in rng ts holds
P1[t] ) holds
P1[nt -tree ts]
proof
let nt be Symbol of (DTConMSA F2()); :: thesis: for ts being FinSequence of TS (DTConMSA F2()) st nt ==> roots ts & ( for t being DecoratedTree of st t in rng ts holds
P1[t] ) holds
P1[nt -tree ts]

let ts be FinSequence of TS (DTConMSA F2()); :: thesis: ( nt ==> roots ts & ( for t being DecoratedTree of st t in rng ts holds
P1[t] ) implies P1[nt -tree ts] )

assume that
A5: nt ==> roots ts and
A6: for t being DecoratedTree of st t in rng ts holds
P1[t] ; :: thesis: P1[nt -tree ts]
( nt in { s where s is Symbol of (DTConMSA F2()) : ex n being FinSequence st s ==> n } & NonTerminals (DTConMSA F2()) = { s where s is Symbol of (DTConMSA F2()) : ex n being FinSequence st s ==> n } ) by A5, LANG1:def 3;
then reconsider sy = nt as NonTerminal of (DTConMSA F2()) ;
sy in [:the carrier' of F1(),{the carrier of F1()}:] by Lm5;
then consider o being OperSymbol of F1(), x2 being Element of {the carrier of F1()} such that
A7: sy = [o,x2] by DOMAIN_1:9;
A8: x2 = the carrier of F1() by TARSKI:def 1;
reconsider p = ts as FinSequence of F1() -Terms F2() ;
[o,the carrier of F1()] = Sym o,F2() by MSAFREE:def 11;
then ts is SubtreeSeq of Sym o,F2() by A5, A7, A8, DTCONSTR:def 9;
then reconsider p = p as ArgumentSeq of Sym o,F2() by Def2;
for t being Term of F1(),F2() st t in rng p holds
P1[t] by A6;
hence P1[nt -tree ts] by A2, A7, A8; :: thesis: verum
end;
for t being DecoratedTree of st t in TS (DTConMSA F2()) holds
P1[t] from DTCONSTR:sch 7(A3, A4);
hence for t being Term of F1(),F2() holds P1[t] ; :: thesis: verum