Efficient Approximation of Well-Designed SPARQL Queries

TL;DR

This paper introduces a method to generate approximate SPARQL queries with reduced OPT operation depth, balancing response time and solution accuracy for well-designed patterns.

Contribution

It proposes a novel approach to transform well-designed SPARQL patterns into trees and generate approximate queries by removing less deep optional subtrees.

Findings

Significant reduction in query response time.

Maintained acceptable accuracy levels in approximate queries.

Effective trade-off between speed and precision.

Abstract

Query response time often influences user experience in the real world. However, it possibly takes more time to answer a query with its all exact solutions, especially when it contains the OPT operations since the OPT operation is the least conventional operator in SPARQL. So it becomes essential to make a trade-off between the query response time and the accuracy of their solutions. In this paper, based on the depth of the OPT operation occurring in a query, we propose an approach to obtain its all approximate queries with less depth of the OPT operation. This paper mainly discusses those queries with well-designed patterns since the OPT operation in a well-designed pattern is really "optional". Firstly, we transform a well-designed pattern in OPT normal form into a well-designed tree, whose inner nodes are labeled by OPT operation and leaf nodes are labeled by patterns containing other operations such as the AND operation and the FILTER operation. Secondly, based on this well-designed tree, we remove "optional" well-designed subtrees with less depth of the OPT operation and then obtain approximate queries with different depths of the OPT operation. Finally, we evaluate the approximate query efficiency with the degree of approximation.