Rewrite Closure and CF Hedge Automata

TL;DR

This paper introduces bidimensional context-free hedge automata, extending hedge automata to recognize more complex tree languages, and demonstrates their closure properties under certain rewriting rules, relevant for XML update modeling.

Contribution

It presents a new class of hedge automata with enhanced rewriting capabilities and proves their closure properties under inverse-monadic and extended rewriting rules.

Findings

Recognize a broader class of tree languages.

Closure under rewrite with inverse-monadic rules.

Extension of rewriting rules for XML updates.

Abstract

We introduce an extension of hedge automata called bidimensional context-free hedge automata. The class of unranked ordered tree languages they recognize is shown to be preserved by rewrite closure with inverse-monadic rules. We also extend the parameterized rewriting rules used for modeling the W3C XQuery Update Facility in previous works, by the possibility to insert a new parent node above a given node. We show that the rewrite closure of hedge automata languages with these extended rewriting systems are context-free hedge languages.