A Trichotomy for Regular Trail Queries

03/01/2019
by   Wim Martens, et al.
0

Regular path queries (RPQs) are an essential component of graph query languages. Such queries consider a regular expression r and a directed edge-labeled graph G and search for paths in G for which the sequence of labels is in the language of r. In order to avoid having to consider infinitely many paths, some database engines restrict such paths to be trails, that is, they only consider paths without repeated edges. In this paper we consider the evaluation problem for RPQs under trail semantics, in the case where the expression is fixed. We show that, in this setting, there exists a trichotomy. More precisely, the complexity of RPQ evaluation divides the regular languages into the finite languages, the class Ttract (for which the problem is tractable), and the rest. Interestingly, the tractable class in the trichotomy is larger than for the trichotomy for simple paths, discovered by Bagan, Bonifati, and Groz [PODS 2013]. In addition to this trichotomy result, we also study characterizations of the tractable class, its expressivity, the recognition problem, closure properties, and show how the decision problem can be extended to the enumeration problem, which is relevant to practice.

READ FULL TEXT
research
10/06/2017

Enumeration Problems for Regular Path Queries

Evaluation of regular path queries (RPQs) is a central problem in graph ...
research
11/12/2021

Regular Path Query Evaluation Sharing a Reduced Transitive Closure Based on Graph Reduction

Regular path queries (RPQs) find pairs of vertices of paths satisfying g...
research
07/27/2022

Representing Paths in Graph Database Pattern Matching

Modern graph database query languages such as GQL, SQL/PGQ, and their ac...
research
07/02/2021

Temporal Regular Path Queries

In the last decade, substantial progress has been made towards standardi...
research
04/27/2018

Certified Graph View Maintenance with Regular Datalog

We employ the Coq proof assistant to develop a mechanically-certified fr...
research
12/15/2022

The Complexity of the Shapley Value for Regular Path Queries

A path query extracts vertex tuples from a labeled graph, based on the w...
research
07/13/2017

A Dichotomy on Constrained Topological Sorting

We introduce the constrained topological sorting problem (CTS-problem): ...

Please sign up or login with your details

Forgot password? Click here to reset