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Two-Way Unary Temporal Logic over Trees

Mikolaj Bojanczyk.
We consider a temporal logic EF+F^-1 for unranked, unordered finite trees. The logic has two operators: EF\phi, which says "in some proper descendant \phi holds", and F^-1\phi, which says "in some proper ancestor \phi holds". We present an algorithm for deciding if a regular language of unranked&nbsp;[&hellip;]
Published on August 5, 2009

Undecidability of a weak version of MSO+U

Mikołaj Bojańczyk ; Laure Daviaud ; Bruno Guillon ; Vincent Penelle ; A. V. Sreejith.
We prove the undecidability of MSO on $\omega$-words extended with the second-order predicate $U_1(X)$ which says that the distance between consecutive positions in a set $X \subseteq \mathbb{N}$ is unbounded. This is achieved by showing that adding $U_1$ to MSO gives a logic with the same&nbsp;[&hellip;]
Published on February 11, 2020

Boundedness in languages of infinite words

Mikołaj Bojańczyk ; Thomas Colcombet.
We define a new class of languages of $\omega$-words, strictly extending $\omega$-regular languages. One way to present this new class is by a type of regular expressions. The new expressions are an extension of $\omega$-regular expressions where two new variants of the Kleene star $L^*$ are&nbsp;[&hellip;]
Published on October 26, 2017

Optimizing tree decompositions in MSO

Mikołaj Bojańczyk ; Michał Pilipczuk.
The classic algorithm of Bodlaender and Kloks [J. Algorithms, 1996] solves the following problem in linear fixed-parameter time: given a tree decomposition of a graph of (possibly suboptimal) width k, compute an optimum-width tree decomposition of the graph. In this work, we prove that this problem&nbsp;[&hellip;]
Published on February 3, 2022

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