5 results
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
Diego Figueira ; Luc Segoufin.
A data tree is a finite tree whose every node carries a label from a finite alphabet and a datum from some infinite domain. We introduce a new model of automata over unranked data trees with a decidable emptiness problem. It is essentially a bottom-up alternating automaton with one register that can […]
Published on November 6, 2017
Nathan Grosshans ; Pierre Mckenzie ; Luc Segoufin.
The program-over-monoid model of computation originates with Barrington's proof that the model captures the complexity class $\mathsf{NC^1}$. Here we make progress in understanding the subtleties of the model. First, we identify a new tameness condition on a class of monoids that entails a natural […]
Published on August 2, 2022
Arnaud Durand ; Nicole Schweikardt ; Luc Segoufin.
A class of relational databases has low degree if for all $\delta>0$, all but finitely many databases in the class have degree at most $n^{\delta}$, where $n$ is the size of the database. Typical examples are databases of bounded degree or of degree bounded by $\log n$. It is known that over a […]
Published on May 10, 2022