Adding Logical Operators to Tree Pattern Queries on Graph-Structured Data

TL;DR

This paper introduces generalized tree pattern queries with logical operators on graph-structured data, providing new algorithms and representations that significantly improve query evaluation efficiency.

Contribution

It proposes GTPQs supporting propositional logic, analyzes their fundamental problems, and develops efficient algorithms with experimental validation.

Findings

GTPQs support full propositional logic for structural constraints.

The proposed algorithms outperform existing methods by several times to orders of magnitude.

Experimental results confirm the effectiveness and efficiency of the approach.

Abstract

As data are increasingly modeled as graphs for expressing complex relationships, the tree pattern query on graph-structured data becomes an important type of queries in real-world applications. Most practical query languages, such as XQuery and SPARQL, support logical expressions using logical-AND/OR/NOT operators to define structural constraints of tree patterns. In this paper, (1) we propose generalized tree pattern queries (GTPQs) over graph-structured data, which fully support propositional logic of structural constraints. (2) We make a thorough study of fundamental problems including satisfiability, containment and minimization, and analyze the computational complexity and the decision procedures of these problems. (3) We propose a compact graph representation of intermediate results and a pruning approach to reduce the size of intermediate results and the number of join operations -- two factors that often impair the efficiency of traditional algorithms for evaluating tree pattern queries. (4) We present an efficient algorithm for evaluating GTPQs using 3-hop as the underlying reachability index. (5) Experiments on both real-life and synthetic data sets demonstrate the effectiveness and efficiency of our algorithm, from several times to orders of magnitude faster than state-of-the-art algorithms in terms of evaluation time, even for traditional tree pattern queries with only conjunctive operations.