Boosting Pushdown and Queue Machines by Preprocessing

Motivated by preprocessing devices occurring for example in the context of syntactic parsers or HTML sanitization, we study pairs of finite state transducers and deterministic machines such as pushdown automata or queue automata as language accepting devices, where the original input is translated by a finite state transducer to an input of the deterministic machine which eventually accepts or rejects the preprocessed input. As deterministic machines we study input-driven machines as well as reversible machines equipped with a pushdown store or a queue store. It turns out that the preprocessing boosts on the one hand the computational power of the machines in all four cases, but on the other hand preserves and adds some positive closure properties as well as decidable problems. Thus, the preprocessing extends the computational power moderately by retaining most of the nice properties of the original machine.