# Programming with Timespans in Interactive Visualizations

## TL;DR

This paper introduces DIEL, a declarative programming model that simplifies the development of interactive visualizations by managing concurrency and interface state through declarative queries over event history.

## Contribution

The paper presents DIEL, a novel declarative framework that helps developers handle concurrency issues in interactive visualizations more easily.

## Key findings

- DIEL reduces code complexity for managing concurrency.
- Developers can specify interface states declaratively instead of procedural updates.
- Conflict resolution in visualizations can be achieved with minimal code.

## Abstract

Modern interactive visualizations are akin to distributed systems, where user interactions, background data processing, remote requests, and streaming data read and modify the interface at the same time. This concurrency is crucial to provide an interactive user experience---forbidding it can cripple responsiveness. However, it is notoriously challenging to program distributed systems, and concurrency can easily lead to ambiguous or confusing interface behaviors. In this paper, we present DIEL, a declarative programming model to help developers reason about and reconcile concurrency-related issues. Using DIEL, developers no longer need to procedurally describe how the interface should update based on different input events, but rather declaratively specify what the state of the interface should be as queries over event history. We show that resolving conflicts from concurrent processes in real-world interactive visualizations can be done in a few lines of DIEL code.