Graph databases are currently one of the most popular paradigms for storing data. One of
the key conceptual differences between graph and relational databases is the focus on …

We study rewritability of monadic disjunctive Datalog programs,(the complements of)
MMSNP sentences, and ontology-mediated queries (OMQs) based on expressive …

Navigational queries over RDF data are viewed as one of the main applications of graph
query languages, and yet the standard model of graph databases—essentially labeled …

We consider entailment problems involving powerful constraint languages such as frontier-
guarded existential rules in which we impose additional semantic restrictions on a set of …

Among the most expressive knowledge representation formalisms are the description logics
of the Z family. For well-behaved fragments of ZOIQ, entailment of positive two-way regular …

The chase procedure is a fundamental algorithmic tool in database theory with a variety of
applications. A central problem concerning the chase procedure is uniform (aka all …

Semantic data fuels many different applications, but is still lacking proper integration into
programming languages. Untyped access is error-prone. Map** approaches cannot fully …

We study query containment in three closely related formalisms: monadic disjunctive
Datalog (MDDLog), MMSNP (a logical generalization of constraint satisfaction problems) …

Guardedness restrictions are one of the principal means to obtain decidable logics---
operators such as negation are restricted so that the free variables are contained in an atom …

Conjunctive query answering over databases with constraints–also known as (tuple-
generating) dependencies–is considered a central database task. To this end, several …