An extended tree transducer (for short: XTT) 6 is a system M = (Q, Σ, ∆, I, R) where • Q is a finite set of states, • Σ and ∆ are alphabets of input and output symbols, respectively, • I ⊆ Q is a set of initial states, and • R is a finite set of rules of the form  where we usually • add the state q as root node of the left-hand side 7 , and • add the states q 1 , .
many standard algorithms for STAG can easily be derived from the corresponding algorithms for STSG.