# Visualizing Intertwined Trees

Due:  Thurs March 22, in class.

The goal of this homework is to gain practice in designing new visualizations for new problems by rapid brainstorming and sketching.  Your assignment is to produce a design for a visualization of intertwined trees.  The research literature is remarkably limited on this particular problem.

The data:  The general problem is as follows.  A set of nodes is simultaneously contained in multiple different tree structures.  A node might be a leaf in one tree and an internal in another tree.  The same node might have different children and a different parent in different trees.  Trees may have different root nodes.  Any given tree does not necessarily contain all the nodes.  Every node is in at least one tree.  You should consider the effect of large number of nodes and large number of trees.  Examples of this problem are:

• A business might organize its people into several  trees:  a boss-employee hierarchy, a project hierarchy, an office location hierarchy, a phone directory structure, or years of service.
• Classification taxonomies:  for example, the topics of a course on Information Visualization might be organized in a number of tree structures.  Topics might be organized by different types of data spaces, interaction strategies, or views, or even by calendar.

The tasks:  Your visualization should help users understand the relationships between trees.  Typical questions might include:

• where does node x fit into the different trees?  (e.g. who are all my different bosses?  whats my shortest path to a root?)
• what is the relationship between nodes x and y in the different trees?   (am i my boss's boss?)
• does a group of nodes stay together across the different trees?
• do trees share any significant portions of structure?  (e.g. boss-employee tree and project tree are very similar?)
• which nodes are most prominent in the different trees?
• how to the structure of the trees compare?  (e.g. broad-shallow vs narrow-deep?)

What to hand in:  About 2 pages describing your proposed solution visualization as follows:

• 1 page of pictures.  These can be hand-drawn with pencil and paper.  The intent here is low-fidelity rapid prototyping, not development.
• 1 page of description.  This should be typed.  Include:
• Describe the pictures and interaction as needed.
• Describe how far your solution scales up (how many nodes, how many trees).
• Describe what is good and bad about your solution, and any tradeoff choices you made (no solution solves everything!).

How you will be graded:  The criteria for grading are:

• Creativity:  original and novel designs demonstrating creative thinking will be rewarded.  I don't want to see Spotfire.
• Utility:  whether your solution will be effective, especially regarding the above tasks.
• Lucidity:  Make sure that your pictures and description are very clear so that I can understand what your visualization means and how the interaction works.  If I can't understand it, I can't give it a good grade.
• Analysis:  whether you understand the limits of your solution and tradeoff decisions.

!Important:  Focus your time on thinking and dreaming up designs.  Don't waste your time trying to draw it in powerpoint or making it functional.