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ally applicable techniques that realize complex pointing intentions” by engaging
“pre-attentive vision in the service of cognitive tasks.”
A standard way to point in a visualization is brushing: selecting and high-
lighting a subset of the data. Naturally, these selections should be sharable as
part of the state of the visualization. In addition, a palette of visual effects richer
than simple highlighting can let users communicate different intents. For exam-
ple, following time-varying values of selected items in a scatter plot is easier
when the selected items leave trails as they move over time. The selected items
and their trails are even more salient if non-selected items are simultaneously
de-emphasized. Brushing-based forms of pointing have the advantage that the
pointing action is tied directly to the data, allowing the same pointing gesture
to be reapplied in different views of the same data. As “data-aware” annotations
are machine-readable, they can also be used to export subsets of data and help
steer automated data mining [108].
Freeform graphical annotations are a more expressive method of pointing in
visualizations. Drawing a circle around a cluster of items or pointing an arrow at
a peak in a graph can direct the attention of remote viewers; at the same time,
the angle of the arrow or shape of the hand-drawn circle may communicate emo-
tional cues or add emphasis. However, while such drawing and vector graphic
annotations allow a high degree of expression, they only apply to a single view
in the visualization, without any explicit tie to the underlying data. Freeform
annotations can persist over purely visual transformations such as panning and
zooming, but they are not data-aware and may become meaningless in the face
of data-oriented operations such as filtering or drill-down. A promising research
direction is hybrid approaches that combine aspects of both brushing and graph-
ical annotation. The resulting techniques could create graphical annotations that
are tied to data points so that they can be reapplied in other views of the data.
Presentation, Dissemination, and Story-Telling:
Common forms of infor-
mation exchange in group sensemaking are reports and presentations. Narrative
presentation of an analysis “story” is a natural and often effective way to commu-
nicate findings, and has been observed as a primary use of Decision Site Posters.
Furthermore, usage of Swivel, sense.us, and Many Eyes leverages external me-
dia such as blogs and social bookmarking services as additional communication
channels in which to share and discuss findings from visualizations. The challenge
to collaborative visualization is to provide mechanisms to aid the creation and
distribution of presentations. For example, sense.us [46] allows users to construct
and share trails of related views to create tours spanning multiple visualizations
and the GeoTime Stories [32] system supports textual story-telling with hyper-
links to visualization states and annotations. However, neither system yet allows
these stories to be exported outside the respective applications. In future work,
such mechanisms could be improved with support to build presentations semi-
automatically using interaction histories, export such presentations into external
media, and apply previously discussed pointing techniques. A related issue is to
enable follow-up analysis and verification for parts of the analysis story, enabling
presentations to serve as a catalyst for additional investigation.
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