Tree-Maps: A Space-Filling Approach to the Visualization of Hierarchical Information Structures Presented by: Daniel Loewus-Deitch

Introduction Novel method for visualizing hierarchies. –Makes 100% use of available space Maps the full hierarchy onto the screen in a “space-filling manner.” –Called Tree-Maps Interactive Control –Allows users to specify presentation of both structural and content information

Introduction Sections of hierarchy with more important information are allocated more display space. Collection of rectangular boxes represent the tree structure. Best suited to hierarchies where –The content of the leaf nodes and the structure of the hierarchy are most important. –The content information associated with internal nodes is largely derived from their children.

Main Objectives Efficient space utilization InteractivityComprehensionEsthetics

Motivation (Problems with Current Methods) Traditional methods for displaying hierarchies can be classified into 3 categories: –Listings –Outlines –Tree diagrams

Listings Can provide detailed content information. Present structural information poorly. –Requires users to parse path information and move manually through the hierarchy to get a real idea of its structure.

Outlines Can nicely provide both structural and content. Structure can only be viewed a few lines at a time. Inadequate for displaying a hierarchical structure with more than a few hundred nodes.

Tree Diagrams Excellent for small structures. Make poor use of available display space. –Too much space used up for background. Little content information. –Presenting additional information clutters the display space.

Why Tree-Maps are a good alternative They use display space efficiently. Can provide structural information implicitly. –Eliminates the need to draw internal nodes. Provide an overall (global) view of the entire hierarchy. –Makes navigation and orientation easier. Provides creative visual cues to communicate content information.

Presenting Directories Problems with current methods: –None provide a graphical representation of the relative sizes of files or directories. –Command line listings force user to piece directory tree together manually. –Windows obscure each other and require too much effort to be arranged in any kind of useful manner. –Icons only show the type of the file, but no other properties.

Presenting Directories Origin of Tree-Maps concept –Venn diagrams –Tree diagrams –Because these waste space, decided to use boxes instead of ovals, along with a bin- packing algorithm. –Worked well for small hierarchies only. Nesting caused problems.

Presenting Directories Origin of Tree-Maps concept –Discovered “slice and dice” method. Simple linear method (top-down). –Developed a weight-proportionate distribution. –Added a pop-up dialog window for detailed content information. –Simple color mapping helps distinguish various properties of files, such as type and size.

Tree Map Method Structural Information: –Interactive approach gives user control over how tree is displayed. –Requires that a weight be assigned to each node, which determines the size of that node’s bounding box.

Tree Map Method Structural Information: –There are some properties that always hold, maintaining a consistent relationship between the structure of the hierarchy and its Tree- Map representation (pg. 156). –Structural information is implicitly presented, but can be nested to explicitly indicate. –Non-nested display explicity provides direct selection only for leaf nodes.

Tree Map Method Content Information: –Variety of display properties determines how the node is drawn. –Color is the most important property. –Other properties include pitch of tone and color saturation. –Pop-up display provides information about the node currently under the cursor.

Coping With Size Groups of small files can become indistinguishable (completely black regions). Zooming in on these regions helps the local structure become clear.

Future Research Exploration of alternate structural partitioning schemes. Appropriate visual display of both numeric and non-numeric content information. Dynamic views –Animated time slice

Future Research Extended operations –Zooming –Marking –Selecting –Searching

Space-Filling Software Visualization Presented by: Daniel Loewus-Deitch

Introduction SeeSys is a system that allows users to visualize statistics associated with code that is divided hierarchically into subsystems, directories, and files.

Introduction Problems with current methods: –Ineffective for large software systems. –Routines for producing flow charts, function call graphs, and structure diagrams often break down. –Incomprehensible, cluttered display.

Introduction Project managers need a tool that facilitates management issues of software development. –Where new development activity is occurring. –Which modules are error prone. Motivation for SeeSys came from AT&T’s massive communications software system. Five questions for project managers (pg. 162)

Introduction Statistical methods, alone, don’t provide the context necessary to make valid analyses. SeeSys visualizes subsystem, directory, and file statistics, but within appropriate context. –Preserves hierarchical relationships in the code. –Makes it easy to relate the statistics to the components.

Approach Based on idea that software system can be decomposed into its individual components. Subsystems labeled with letters. Subsystems are partitioned vertically and their area is based on a particular subsystem statistic. Allows for visual comparison of directories within a subsystem.

Approach Fill represents a second statistic, such as indicating newly-developed code. Zoom view to get a closer look at an individual subsystem. Hierarchical decomposition immediately relates the files to their directories and the directories to their subsystems. –Makes cross unit comparisons easy.

Approach The fill represents percentages. –Allows for quick discovery of outliers.

Applications Subsystem information –Size and color brightness represent the size or individual subsystems. Directory information –Each subsystem is partitioned vertically to show its internal directories. –Area and color represent size. –Fill is related to new development. –Figure 3 is the “software skyline.”

Applications Error-prone code –Directory spikes represent detail for directory bug fixing. –Subsystem g shows an example of a very high bug rate (figure 5), represented by the light gray subsystem rectangle. System evolution –Animated display portrays growth through the software’s version releases. –Shows history and trends of each subsystem.

The Visualization System SeeSys was designed to display software metrics that have two properties –Quantitative measure –Additive May be extended to display complexity metrics.

User Interaction Tracks mouse movements and shows extra information about the component that the mouse cursor is touching. –Active component indicated by a red highlighted boundary. Available stats are shown on lower left side of screen. Clicking these stats creates a redrawn display focused on this particular statistic.

User Interaction Five buttons control various options such as presence of fill and zoom activation. ROWS slider controls the number of rows in the display. Speed slider and frame slider control animation. During animation, one can watch the active bar in the slider to see that particular subsystem’s evolution.

Display Principles Based on 3 principles: –Individual components can be assembled to form the whole. Allows users to see relationships between components. –Pairs of components can be compared. –Components can be disassembled into smaller components. Allows structure of display to reflect structure of software.

Screen Real-Estate 100% of display area is utilized. Components with large statistics are visually dominant. Zoom feature allows user to see small directories.

Spatial Relationships Takes advantage of human ability to recognize spatial relationships. People relate each component to the whole. It is easier to see relationships between components if the heights of the rectangles are equal. –Row slider allows user to choose number of rows displayed for an optimal display.

Color Redundantly encodes size. Can also be used to encode age, complexity, activity, number of programmers, etc.

Implementation Four linked views of data: –Colorful space-filling display. –Leftspace – controls, buttons, sliders. –Bottomspace – color scale and statistics. –Zoom view – details of a particular subsystem.

Summary SeeSys provides the following utilities: –Shows the sizes of the subsystems and directories and where the recent activity has occurred. –Zoom in on particular subsystems. –Explore where bug fixes and new functionality have occurred. –Identify directories and subsystems with high fix-on-fix rates. –Find historically active and extinct subsystems

Summary 3 principles should ultimately be observed when designing any visualization system for large software systems: –Structure of display should reflect structure of software. –Individual components should by comparable and decomposable. –Animation helps user visualize the evolution of the software.

Summary Potential users of SeeSys: –Project managers –Feature engineers –Software developers