Handbook of formal languages, vol. 3
Automata, Languages, and Machines
Automata, Languages, and Machines
A Framework for Studying Grammars
Proceedings on Mathematical Foundations of Computer Science
The First-Order Theory of One-Step Rewriting is Undecidable
RTA '96 Proceedings of the 7th International Conference on Rewriting Techniques and Applications
Iterated Length-Preserving Rational Transductions
MFCS '98 Proceedings of the 23rd International Symposium on Mathematical Foundations of Computer Science
Iterated GSM Mappings: A Collapsing Hierarchy
Iterated GSM Mappings: A Collapsing Hierarchy
Shape preserving top-down tree transducers
Theoretical Computer Science
Shape preserving bottom-up tree transducers
Journal of Automata, Languages and Combinatorics
| Hi-index | 5.23 |
In this paper we consider the closure UCI(Rel) of the class of relabeling tree transformations, under U=union, C=composition and I=iteration. We give a characterization of UCI(Rel) in terms of a short expression built up from Rel with composition and iteration. We also give a characterization of UCI(Rel) in terms of one-step rewrite relations of very simple term rewrite systems. We give a similar characterization of UC(FRel+), where FRel+ is the class consisting of the transitive closures of all functional relabeling tree transformations. Finally we show that UCI(Rel)=UCI(FRel).