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Datalog Rewritings of Regular Path Queries using Views

Nadime Francis ; Luc Segoufin ; Cristina Sirangelo.

We consider query answering using views on graph databases, i.e. databases structured as edge-labeled graphs. We mainly consider views and queries specified by Regular Path Queries (RPQ). These are queries selecting pairs of nodes in a graph database that are connected via a path whose sequence of&nbsp;[&hellip;]

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Deciding definability in FO2(<h,<v) on trees

Thomas Place ; Luc Segoufin.

We provide a decidable characterization of regular forest languages definable in FO2(<h,<v). By FO2(<h,<v) we refer to the two variable fragment of first order logic built from the descendant relation and the following sibling relation. In terms of expressive power it corresponds to a fragment of&nbsp;[&hellip;]

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First-order queries on classes of structures with bounded expansion

Wojtek Kazana ; Luc Segoufin.

We consider the evaluation of first-order queries over classes of databases with bounded expansion. The notion of bounded expansion is fairly broad and generalizes bounded degree, bounded treewidth and exclusion of at least one minor. It was known that over a class of databases with bounded&nbsp;[&hellip;]

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Enumerating Answers to First-Order Queries over Databases of Low Degree

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&nbsp;[&hellip;]

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Tameness and the power of programs over monoids in DA

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&nbsp;[&hellip;]

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