Grammar-based Compression of Unranked Trees
Data Structures and Algorithms
2018-02-16 v1 Formal Languages and Automata Theory
Abstract
We introduce forest straight-line programs (FSLPs) as a compressed representation of unranked ordered node-labelled trees. FSLPs are based on the operations of forest algebra and generalize tree straight-line programs. We compare the succinctness of FSLPs with two other compression schemes for unranked trees: top dags and tree straight-line programs of first-child/next sibling encodings. Efficient translations between these formalisms are provided. Finally, we show that equality of unranked trees in the setting where certain symbols are associative or commutative can be tested in polynomial time. This generalizes previous results for testing isomorphism of compressed unordered ranked trees.
Keywords
Cite
@article{arxiv.1802.05490,
title = {Grammar-based Compression of Unranked Trees},
author = {Adrià Gascón and Markus Lohrey and Sebastian Maneth and Carl Philipp Reh and Kurt Sieber},
journal= {arXiv preprint arXiv:1802.05490},
year = {2018}
}
Comments
Extended version of a paper at CSR 2018