Figure 2: The excerpt of the zoomed in drawing view.
A filter in Tom Sawyer Perspectives is basically
a set of conditions. Only the data satisfy the
conditions of the filter will be populated.
A filter is added to the project to investigate the
temporal generation of this series of tweets. The
condition for the User elements is that the
TimeStamp attribute is less than CurrentTime. The
condition for the Status elements is similar. A slider,
as shown in Figure 3, controls the value of
CurrentTime.
Figure 3: The filter.
If the user moves the slider to the left most, the
earliest posts during this time period will display. If
the slider is put at the right most, all the information
from the data source will be displayed (see Figure
1).
Instead of viewing all the tweets in one big
picture, we can explore the tweets generation
process. Who posted the first one? Who replied?
These are all clear in the drawing view.
3.3.4 Multiple Views
Graphs are a good solution for visualizing social
networks. However, due to the large size and the
limitation of resolution and screen size of
computers, social network graphs usually end up
cluttered and rather illegible (Viegas and Donath,
2004). One good method in visual analytics is to use
coordinated and multiple views (Roberts, 2007).
Tom Sawyer Perspectives provides multiple
views, including drawings, tables, trees, and
inspectors. Thus we can easily analyze data from
different perspectives.
Besides the drawing view we already discussed,
we add two table views and an inspector view to the
project, as shown in Figure 4.
The drawing view graphically represents the
tweets related to “visualization”. In the drawing
view, the relationships among users and tweets
become quite clear and it also gives us a big picture
of what’s going on in that time period. The table
views provide a more organized perspective of the
data. Each user or tweet is listed in the table as a
record. We can also sort the data by any column. For
example, messages can be sorted by their time
stamps. The inspector view focuses on one particular
element and offers more details. In Figure 4, the
view displays the attribute values of user
“numeroteca”.
The synchronized selection and highlighting
integrate multiple views seamlessly in a single
project so that we can better explore and understand
the structure, relationship and semantics of the social
network.
3.3.5 Search
How to locate a particular actor from a large number
of nodes in a social network graph? This doesn’t
sound to be an easy task unless we can search on the
graph. In Tom Sawyer Perspectives, a search
configuration enables searching for specific model
elements based on the values of specific attributes of
the model elements.
With the help of the search feature, users can
quickly look for particular information in the large
social network. If we want to find out whether
someone named “Andrew” posted visualization
related messages during our interested time frame,
just type “Andrew” in the search box at the top right
corner of the drawing view. The matched nodes will
then be highlighted.
3.3.6 Animation
In section 3.3.3, we described the capability of
filtering the messages according to their posted time
stamps. We can even improve this by enabling
animation. When pressing the Play button (as shown
in Figure 3), the slider will automatically move from
left to right, and the filter condition changes
accordingly. The tweets generation process will be
shown like a movie in the drawing view. Temporal
reasoning provides a good way to explore the
network over time, gives us clues of the
development and trend of the social network which
will be critical in decision making.
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