PIWD: A Plugin-based Framework for Well-Designed SPARQL

TL;DR

PIWD is a plugin-based framework that efficiently evaluates SPARQL queries built on well-designed patterns containing AND and OPT operators by transforming them into a tree structure and leveraging existing query engines.

Contribution

The paper introduces a novel plugin-based framework, PIWD, for evaluating WDAO-patterns in SPARQL queries using a well-designed tree structure and transformation techniques.

Findings

PIWD effectively evaluates WDAO-pattern queries.

The framework reduces query evaluation to subgraph homomorphism.

Preliminary experiments show good efficiency on gStore and RDF-3X.

Abstract

In the real world datasets (e.g.,DBpedia query log), queries built on well-designed patterns containing only AND and OPT operators (for short, WDAO-patterns) account for a large proportion among all SPARQL queries. In this paper, we present a plugin-based framework for all SELECT queries built on WDAO-patterns, named PIWD. The framework is based on a parse tree called \emph{well-designed AND-OPT tree} (for short, WDAO-tree) whose leaves are basic graph patterns (BGP) and inner nodes are the OPT operators. We prove that for any WDAO-pattern, its parse tree can be equivalently transformed into a WDAO-tree. Based on the proposed framework, we can employ any query engine to evaluate BGP for evaluating queries built on WDAO-patterns in a convenient way. Theoretically, we can reduce the query evaluation of WDAO-patterns to subgraph homomorphism as well as BGP since the query evaluation of BGP is equivalent to subgraph homomorphism. Finally, our preliminary experiments on gStore and RDF-3X show that PIWD can answer all queries built on WDAO-patterns effectively and efficiently.