License: Creative Commons Attribution 3.0 Unported license (CC BY 3.0)
When quoting this document, please refer to the following
DOI: 10.4230/LIPIcs.ICDT.2017.18
URN: urn:nbn:de:0030-drops-70584
Go to the corresponding LIPIcs Volume Portal

Lohrey, Markus ; Maneth, Sebastian ; Reh, Carl Philipp

Compression of Unordered XML Trees

LIPIcs-ICDT-2017-18.pdf (0.5 MB)


Many XML documents are data-centric and do not make use of the inherent document order. Can we provide stronger compression for such documents through giving up order? We first consider compression via minimal dags (directed acyclic graphs) and study the worst case ratio of the size of the ordered dag divided by the size of the unordered dag, where the worst case is taken for all trees of size n. We prove that this worst case ratio is n / log n for the edge size and n log log n / log n for the node size. In experiments we compare several known compressors on the original document tree versus on a canonical version obtained by length-lexicographical sorting of subtrees. For some documents this difference is surprisingly large: reverse binary dags can be smaller by a factor of 3.7 and other compressors can be smaller by factors of up to 190.

BibTeX - Entry

  author =	{Markus Lohrey and Sebastian Maneth and Carl Philipp Reh},
  title =	{{Compression of Unordered XML Trees}},
  booktitle =	{20th International Conference on Database Theory (ICDT 2017)},
  pages =	{18:1--18:17},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-024-8},
  ISSN =	{1868-8969},
  year =	{2017},
  volume =	{68},
  editor =	{Michael Benedikt and Giorgio Orsi},
  publisher =	{Schloss Dagstuhl--Leibniz-Zentrum fuer Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{},
  URN =		{urn:nbn:de:0030-drops-70584},
  doi =		{10.4230/LIPIcs.ICDT.2017.18},
  annote =	{Keywords: tree compression, directed acyclic graphs, XML}

Keywords: tree compression, directed acyclic graphs, XML
Collection: 20th International Conference on Database Theory (ICDT 2017)
Issue Date: 2017
Date of publication: 17.03.2017

DROPS-Home | Fulltext Search | Imprint | Privacy Published by LZI