Preservation of Recognizability for Synchronous Tree Substitution Grammars

Zoltán Fülöp, Andreas Maletti, Heiko Vogler

Abstract: We consider synchronous tree substitution grammars (Stsg). With the help of a characterization of the expressive power of Stsg in terms of weighted tree bimorphisms, we show that both the forward and the backward application of an Stsg preserve recognizability of weighted tree languages in all reasonable cases. As a consequence, both the domain and the range of an Stsg without chain rules are recognizable weighted tree languages.