Visualization

Displaying a Model at a Single Time Step

A single time step of a linked model corresponds to a group of entities and their known or implied relationships at a particular time.  It is natural to represent linked data as graphs, with nodes corresponding to entities and arcs corresponding to relations. The graphs will be visualized in 2D or 3D display space as glyphs linked by arcs.  The visual characteristics of both glyphs and arcs, such as position, color, size, shape, texture, and style, can be varied to convey patterns embedded in the data. The visualization tools must be able to represent the uncertainty of the entities and their relationships.

When sufficient information about analyst interest is available, these mappings can be made in a way that maximizes the visual impact of items or characteristics of particular interest. For example, items of interest might be represented in a larger size, more vivid color, greater detail, or differentiated style. The goal is to provide the correct level of detail for each part of the display, conveying both fine detail and overall context.

Interacting with the Visual Representation 

The system provides flexible facilities for the user to specify how object characteristics will be mapped to visual characteristics, such as the color, size and the shape of visual elements. For example, an user might make the glyphs representing the most influential researchers in a field and show the research area by color. In the resulting display, the activity of the major subjects would be more perceptually salient, and interactions between research areas would appear as dynamic blending of colors. The system also provide the facilities for users to specify the interested objects and display the different objects in  different degree of detail.

In addition, the system allow users to dynamically re-arrange objects to enhance or de-emphasize the perceptual salience of their proximity. For example, if the user decides at some point that they are primarily interested in the roles of two particular people in a certain scientific community, those two people can be placed prominently in the foreground far apart to perceptually accentuate their links and activity.

Showing Changes over Time

The system implements mechanisms that allow the user to explore the changing structure of the linked data. Change representation mechanisms support the clear display of the individual step or states, as well as the explicit differences between them. Changes in the data is conducted through animation, interaction, and inclusion of trend and difference information in individual views.

Animation is the most straightforward way to show changing patterns. Each frame corresponds to a model at a particular time and movement of objects in the animation corresponds to changes in the underlying relational data. Given the spatial arrangement of objects, an animation will show motion that corresponds to changes in the objects and their relations. For example, if Professor X and Professor Y begin to cite the same papers and got to the same conferences, they will be moved closer together. If, on the other hand, their research begins to diverge, they will be moved farther apart. In addition to changing position, other visual attributes might change as the values that the represent change. At any time, the user will be able to pause the animation to drill down into the data underlying the current frame, and will be able to play the animation at different frame rates in both forward and reverse directions.

Additionally, we will explore methods for capturing change and difference in a snapshot, such as those inspired by the motion blur seen in photographs of moving objects. The glyph representing an object at one time step might be shown with a trail showing where it has been (or will be). The goal is to convey some sense of the dynamics of the changing structure in a single image that can be incorporated in presentations or simply sent electronically to others.