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.
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.
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.
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