Alphabetic and synchronized tree transducers

Abstract

We define a new type of tree transducers. The family of transformations computed by them is exactly the family of alphabetic tree relations. We call these transducers alphabetic. By taking synchronized computations on an alphabetic transducer, we derive a new type of relation which is called synchronized. We show that the class SAT of synchronized relations properly contains the class AT of alphabetic relations. Moreover, SAT is incomparable with both the families of top-down T-FST and bottom-up B-FST tree transductions.