FUTURE DIRECTIONS

Zoomology is an overview/detail solution for comparing large hierarchical trees. A single overview window shows broad areas of change and provides context and location, while twin zooming detail windows allow discovery of low-level differences. Although a powerful tool in its current incarnation, additional work remains.

Current limitations:

Individual nodes cannot be selected at lower levels of the overview.

Areas at the lower levels of the overview may misrepresent the number and rank of nodes.

Change is represented as a white area, thus loss of rank information is experienced.

No distinction is made between nodes present in dataset A but not in set B, nor are the ranks of nodes distinguishable.

There is no way to discern between minor changes such as the insertion of a single node and major revisions such as changes throughout an entire branch.

There is no indication of qualitative vs. quantitative change.

The detail view cannot compare substructures spanning multiple levels.

In the detail view, size does not map to number of descendants.

Possible solutions

Intermediate Overview

Allowing the user to enlarge parts of the tree structure in the overview would ease some of the problems we have seen at the overview’s lower levels. It would allow accurate mapping of size and color for lower-level nodes. Enlargement of such nodes would allow the user to select them for detail view. Areas of difference between trees could be colored to indicate rank and bordered to represent the tree of origin. An intermediate overview would allow the user to identify all nodes that share a common name and could aid comparison of subtrees.

Predictive text entry

This or a fisheye-based table of contents could eliminate misspellings, a common occurence due to the similarities in scientific names.

Usability Testing

While using Zoomology, a biologist clicked on the colored legend between the two detail views with the intent of navigating to a different level in the detail views. Incorporating this feature would require an unlinking of views, since not all of a given rank is located at the same zoom level in both datasets. It would also require a method of highlighting for values of the selected rank that are nested too deeply into other levels to see.

Increased Task Conformance

The current application arbitrarily begins ordering alphabetically, and the horizontal position/location of data in the overview is meaningless. Users may benefit from a preferences palette or menu, enabling control of more significant meta-organization from left to right.

Expandable Overview

Zooming on the overview along the x-axis may be effective in dealing with the compressed data while still maintaining context.