Databases Reference
In-Depth Information
Figure 3.1:
The Snow's drawing.
tation of that data (e.g., plotting deaths in the location in which they happened), and present it to
the end user (e.g., producing a drawing like the one on Figure
3.3
).
However, these steps are inherently static and do not easily scale to different data sets, repre-
sentations, or presentations; conversely, the availability of a computer that allows for interactive data
manipulation and transformation introduces new possibilities and new challenges. As an example,
assume that Dr. Snow's target analysis covered the whole of London. In such a case, it is almost
impossible to have a hand-drawing of the whole city, but it is a task that is trivial using a computer.
On the other hand, how to
present
such a large map on a computer screen? Usual pan and zoom
facilities are not enough, and new strategies are required.
As a more complex example, assume that we want to use colors to visualize, for each death,
the closest pump. The calculation associated with this new
representation
is time consuming for a
human-based drawing but can be easily implemented in a computer-based visualization. Moreover,
it is worth noting that this information was not present in the original data, and it is a nice example
of the kinds of
elaboration
that can produce better visualizations.
The above considerations lead to focus on three main issues: data extraction and elaboration,
data representation, and data presentation, discussed in the following subsection.
