Counting in trees for free

Helmut Seidl, Thomas Schwentick, Anca Muscholl, Peter Habermehl

Research output: Chapter in Book/Report/Conference proceedingChapterpeer-review

70 Scopus citations

Abstract

It is known that MSO logic for ordered unranked trees is undecidable if Presburger constraints are allowed at children of nodes. We show here that a decidable logic is obtained if we use a modal fixpoint logic instead. We present a characterization of this logic by means of deterministic Presburger tree automata and show how it can be used to express numerical document queries. Surprisingly, the complexity of satisfiability for the extended logic is asymptotically the same as for the original fixpoint logic. The non-emptiness for Presburger tree automata (PTA) is PSPACE-complete, which is moderate given that it is already PSPACE-hard to test whether the complement of a regular expression is non-empty. We also identify a subclass of PTAs with a tractable non-emptiness problem. Further, to decide whether a tree t satisfies a formula φ is polynomial in the size of φ and linear in the size of t. A technical construction of independent interest is a linear time construction of a Presburger formula for the Parikh image of a regular language.

Original languageEnglish
Title of host publicationLecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)
EditorsJosep Díaz, Juhani Karhumäki, Arto Lepistö, Donald Sannella
PublisherSpringer Verlag
Pages1136-1149
Number of pages14
ISBN (Print)3540228497
DOIs
StatePublished - 2004

Publication series

NameLecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)
Volume3142
ISSN (Print)0302-9743
ISSN (Electronic)1611-3349

Fingerprint

Dive into the research topics of 'Counting in trees for free'. Together they form a unique fingerprint.

Cite this