All You Need Is CONSTRUCT

TL;DR

This paper introduces a formal language for nested SPARQL queries involving CONSTRUCT and SELECT forms, providing a uniform semantics and showing how SELECT can be encoded as CONSTRUCT, advancing query composition understanding.

Contribution

It presents a new formal language for nested SPARQL queries with a unified semantics, enabling encoding of SELECT queries as CONSTRUCT queries.

Findings

Formal semantics for nested SPARQL queries

Encoding of SELECT as CONSTRUCT queries

Extension of RDF graphs to include variables

Abstract

In SPARQL, the query forms SELECT and CONSTRUCT have been the subject of several studies, both theoretical and practical. However, the composition of such queries and their interweaving when forming involved nested queries has not yet received much interest in the literature. We mainly tackle the problem of composing such queries. For this purpose, we introduce a language close to SPARQL where queries can be nested at will, involving either CONSTRUCT or SELECT query forms and provide a formal semantics for it. This semantics is based on a uniform interpretation of queries. This uniformity is due to an extension of the notion of RDF graphs to include isolated items such as variables. As a key feature of this work, we show how classical SELECT queries can be easily encoded as a particular case of CONSTRUCT queries.