Crossroads - Winter 2008

such as 1987 and 1988 in Sri Lanka. Users noted that the 1970’s data seemed exceptionally small, and questioned what the spikes accounted for. All users were curious of why data in 1993 was missing.

Overall, users found the tool easy to learn and use, and were eager to learn more about the underlying data. One user who had previously been exposed to NameVoyager commented that also she enjoyed using the GTD Explorer, it was not as enticing as the NameVoyager data which she was more familiar with and could associate with people around her. Most users also commented on the response time, suggesting that an increased responsiveness would make the tool more usable.

Software Improvements

There are several software improvements that may be made. In the visualization, stripes that have a wide region may be labeled. When dealing with larger data sets, the GTD Explorer can slow down quite a bit. Performance enhancements must be made to keep up with the growing data set.

One feature that was requested by multiple users was a comparison feature. Comparing several arbitrary items is not supported. One possible solution would be to have checkboxes in each row of the details grid. Users can select or deselect items to make corresponding stripes visible or not.

The details grid is convenient when users are searching for details of a particular item. Once they find this item, the corresponding stripes should be highlighted to lead the user.

When using interactive controls, users often want to undo/redo actions. History storing was a feature many users requested for.

Conclusion and Future Work

The GTD Explorer is a Web-based visualization of the Global Terrorism Database, a database that contains data over time. It supports mouse and keyboard interactions to explore the data, and is easily extendable to support different types of data. It has a text search filter, a data count filter, and a detailed information grid which gives an overview of the data in text.

The work in this paper is largely a work in progress, suggesting several issues that remain for future investigation.

First of all, these are issues that are related to the use of temporal data. A time-axis filter could be provided to zoom into specific time slots. A Time Searcher [ 2] style pattern searching feature could be useful in finding similar patterns.

Entity identification and resolution is also a problem. For example, a search for Germany suggests that the country was extremely peaceful until 1990, but a search for West Germany tells a different story. Czecho-slovakia, Czech and Slovak or the Soviet Union and Russia would be other examples. Relating these entities is a problem to be solved.

Users tend to view temporal patterns in light of real world events, such as the Munich Olympics or September 11th World Trade Center attacks. An advanced version of the GTD Explorer could incorporate meaningful event data to offer a more comprehensive view of the data. Allowing public users to annotate the chart could generate interesting outcome.

Also, when the data being displayed is geographical, it would be useful to have a world map view that shows where the incidents occurred using scattered dots. Heat maps may be used if there is much occlusion. The GTD Explorer is a tool developed specifically for the Global Terrorism Database. A general framework that is applicable in visualizing time series or temporal data could be developed to aid future users or data providers. In the future we would like to do

Figure 14: Germany (top) and West Germany (bottom).

an analysis of the social aspects of this tool. Feedback received from Web users should be a valuable source in seeing what drives the users to use this tool and how they use it to communicate information.

Acknowledgments

I appreciate the invaluable guidance of Prof. Ben Shneiderman at the University of Maryland Human Computer Interaction Lab. I am also extremely grateful to Adam Perer for his insight and thoughtful feedback and continued assistance throughout the project.

Many thanks to researchers from START, Gary LaFree, Alex Jonas, Erin Miller, Laura Dugan, Gary Ackerman, Kathleen Smarick. They have provided the Global Terrorism Database and have given opinions as experts on the subject matter. Without either, this project could not have been pursued.

I also thank my fellow graduate students who participated in the user study and provided many useful comments.

References

1. Adobe Flash Player version penetration. http://www.adobe.com/ products/player census/flashplayer/; http://www.adobe.com/ products/player census/flashplayer/version penetration.html.

2. Aris, A., Jank, W., Plaisant, C., Shmueli, G., Shneiderman, B., and Simeone, A. 2007. Similarity-based forecasting with simultaneous previews: A river plot interface for time series forecasting. In Proceedings of the 11th International Conference Information Visualization (IV’07 ), Zurich, Switzerland. IEEE Computer Society. 191-196.