3 results
Mikołaj Bojańczyk ; Luc Segoufin ; Howard Straubing.
This paper presents a decidable characterization of tree languages that can be defined by a boolean combination of Sigma_1 sentences. This is a tree extension of the Simon theorem, which says that a string language can be defined by a boolean combination of Sigma_1 sentences if and only if its […]
Published on September 29, 2012
Florent Jacquemard ; Luc Segoufin ; Jerémie Dimino.
A data tree is an unranked ordered tree where each node carries a label from a finite alphabet and a datum from some infinite domain. We consider the two variable first order logic FO2(<,+1,~) over data trees. Here +1 refers to the child and the next sibling relations while < refers to the […]
Published on April 26, 2016
Mikolaj Bojanczyk ; Luc Segoufin.
We study tree languages that can be defined in \Delta_2 . These are tree languages definable by a first-order formula whose quantifier prefix is forall exists, and simultaneously by a first-order formula whose quantifier prefix is . For the quantifier free part we consider two signatures, either the […]
Published on October 20, 2010