A Comparative Study on Fixed-Order Event Sequence Visualizations: Gantt, Extended Gantt, and Stringline Charts

We conduct two in-lab experiments (N = 93) to evaluate the effectiveness of Gantt charts, extended Gantt charts, and stringline charts for visualizing fixed-order event sequence data. We first formulate five types of event sequences and define three types of sequence elements: point events, interval events, and the temporal gaps between them. Our two experiments focus on event sequences with a pre-defined, fixed order and measure task error rates and completion time. The first experiment shows single sequences and assesses the three charts’ performance in comparing event duration or gap. The second experiment shows multiple sequences and evaluates how well the charts reveal temporal patterns. The results suggest that when visualizing single fixed-order event sequences, 1) Gantt and extended Gantt charts lead to comparable error rates in the duration-comparing task; 2) Gantt charts exhibit either shorter or equal completion time than extended Gantt charts; 3) both Gantt and extended Gantt charts demonstrate shorter completion times than stringline charts; 4) however, stringline charts outperform the other two charts with fewer errors in the comparing task when event type counts are high. Additionally, when visualizing multiple point-based fixed-order event sequences, stringline charts require less time than Gantt charts for people to find temporal patterns. Based on these findings, we discuss design opportunities for visualizing fixed-order event sequences and discuss future avenues for optimizing these charts.

I. Introduction

Fixed-order event sequence is a type of sequence data that exists in various scenarios, such as industrial logs of products in assembly lines [1], [2], [3], [4], [5], traveling records of vehicles in public transportation [6], [7], [8], [9], cascading effects of disaster [10], and biological process like apoptosis [11]. In these event sequences, the order of events is predefined and usually remains consistent in each sequence. This stands different from sequences where events occur in an unpredictable order [12], [13], [14], [15], [16], [17]. To illustrate, consider a scenario of manufacturing a particular product within an industrial workflow. Each stage in this process can be considered as an event that needs to be carried out in a predefined order to complete the manufacturing. In this context, the production process of an individual product is a fixed-order event sequence. Despite the fixed order, the identical steps in different sequences happen at different timestamps and last for different durations. Visualizing such event sequences can provide valuable insights into understanding, troubleshooting, and optimizing production processes.