5 papers
Structural Indexing of Relational Databases for the Evaluation of Free-Connex Acyclic Conjunctive Queries
Cristian Riveros, Benjamin Scheidt, Nicole Schweikardt
We present an index structure to boost the evaluation of free-connex acyclic conjunctive queries (fc-ACQs) over relational databases. The main ingredient of the index associated wi…
Color Refinement for Relational Structures
Benjamin Scheidt, Nicole Schweikardt
Color Refinement, also known as Naive Vertex Classification, is a classical method to distinguish graphs by iteratively computing a coloring of their vertices. While it is mainly u…
Using Color Refinement to Boost Enumeration and Counting for Acyclic CQs of Binary Schemas
Cristian Riveros, Benjamin Scheidt, Nicole Schweikardt
We present an index structure, called the color-index, to boost the evaluation of acyclic conjunctive queries (ACQs) over binary schemas. The color-index is based on the color refi…
On Homomorphism Indistinguishability and Hypertree Depth
Benjamin Scheidt
is a logic introduced by Scheidt and Schweikardt (2023) to express properties of hypergraphs. It is similar to first-order logic with counting quantifiers () adapted to t…
Counting Homomorphisms from Hypergraphs of Bounded Generalised Hypertree Width: A Logical Characterisation
Benjamin Scheidt, Nicole Schweikardt
We introduce the 2-sorted counting logic that expresses properties of hypergraphs. This logic has available k variables to address hyperedges, an unbounded number of variabl…