A Tutorial on Visual Representations of Relational Queries

TL;DR

This paper reviews visual metaphors and diagrammatic representations that help users understand complex relational queries, aiding in query formulation and comprehension in systems like spoken interfaces.

Contribution

It provides a comprehensive survey of historical and modern visual representations of relational queries, linking visual metaphors to relational algebra and calculus.

Findings

Survey of over a century of diagrammatic languages

Mapping visual alphabets to relational algebra and calculus

Analysis of key visual metaphors for relational queries

Abstract

Query formulation is increasingly performed by systems that need to guess a user's intent (e.g. via spoken word interfaces). But how can a user know that the computational agent is returning answers to the "right" query? More generally, given that relational queries can become pretty complicated, how can we help users understand existing relational queries, whether human-generated or automatically generated? Now seems the right moment to revisit a topic that predates the birth of the relational model: developing visual metaphors that help users understand relational queries. This lecture-style tutorial surveys the key visual metaphors developed for visual representations of relational expressions. We will survey the history and state-of-the art of relationally-complete diagrammatic representations of relational queries, discuss the key visual metaphors developed in over a century of investigating diagrammatic languages, and organize the landscape by mapping their used visual alphabets to the syntax and semantics of Relational Algebra (RA) and Relational Calculus (RC).