Multi-Phase Tree Transformations

摘要

In this paper, we introduce a computational model of a tree transducer called a bi-stage transducer and study its properties. We consider a mapping on trees realized by composition of any sequence of top-down transducers and bottom-up transducers, and call such a mapping a multi-phase tree transformation. We think a multi-phase tree transformation is sufficiently powerful. It is shown that in the case of rank-preserving transducers, a multi-phase tree transformation is realized by a bi-stage transducer.