Human-Centered Information Visualization

Jiajie Zhang, Kathy Johnson, Jack Smith

University of Texas at Houston

Jane Malin

NASA Johnson Space Center

July 18, 2002

Dynamic Visualizations and Learning, Tübingen

Information Visualization: What?

• Information visualization is the static or dynamic presentation of information in an external representation such that the information can be processed by efficient human visual mechanisms

• The key idea is to make use of people’s powerful visual system to efficiently process information that otherwise requires more cognitive effort.

Information Visualization: Why?

• Human visual system is powerful because – it can process information in parallel,

automatically, and unconsciously, – it can bypass the bottleneck of human working

memory that is limited in capacity

Information Visualization: Why?

• Nice features of external representations– Provide short-term or long-term memory aids so that

memory load can be reduced.

– Provide information that can be directly perceived and used such that little effortful processing is needed to interpret and formulate the information explicitly.

– Provide knowledge and skills that are unavailable from internal representations

– Support perceptual operators that can recognize features easily and make inferences directly.

Information Visualization: Why?

• Nice features of external representations --more– Anchor and structure cognitive behavior without

conscious awareness.– Change the nature of a task by generating more

efficient action sequences.– Stop time and support perceptual rehearsal to make

invisible and transient information visible and sustainable.

– Aid processibility by limiting abstraction.– Determine decision making strategies through accuracy

maximization and effort minimization.

Information Visualization: How?-- Human-Centered Computing

• Traditionally, visualization is mainly at the level of representations.

• Other levels are also important– Users– Functions– Tasks

• A human-centered approach

Functional Analysis: identify domain structure and ideal task space independent of implementations

User Analysis: identify characteristics of users, such as expertise and skills, knowledge base, age, education, cognitive capacities and limitat ions, perceptual variat ions, etc.

Task Analysis: identify system funct ions that have to be performed, procedures and actions to be carried out, information to be processed, pattern and dynamics of informat ion flow, input and output formats, constraints that must be considered, communicat ion needs, and the organization and structure of the task.

Representational Analysis: identify the best informat ion display format and the best informat ion flow dynamtics for a given task such that the interaction between users and systems is in a d irect interact ion mode.

Contents for S ystem Implementation: Functional requirements; user profiles; hierarchical task structure; information flow diagrams; task-specific, event-related, and context -sensitive informat ion displays; and so on.

User Analysis

• The process of identifying user characteristics– expertise and skills, knowledge base, education

background, cognitive capacities and limitations, perceptual variations, age related skills, cultural background, personality, time available for learning and training, frequency of system use, etc.

– User analysis will help us design visualization systems that have the right knowledge and information structure that match that of the users.

Functional Analysis

• Functional analysis is the process of identifying critical top-level domain structures, goals, and ideal spaces that are largely independent of implementations .

Task Analysis

• Task analysis is the process of identifying – system functions that have to be performed

– procedures to be carried out to achieve task goals

– information to be processed

– input and output formats that are required

– constraints that must be considered

– communication needs that have to be satisfied

– organization and structure

– information categories and information flow

Representational Analysis

• The process of identifying the best information display format for a given task performed by a specific type of users such that the interaction between users and systems is in a direct interaction mode

Coxcomb Polar Plot

D-D•• •

•

Cartesian Plot Line Graph

L-LCrossRectangle

L-A

D-P•• •

•

Cartesian Plot0 0

•• ••

L-O

L-P L-P

PolygonGlyphs

Vertical Bar Chart

Segmented Bar Chart

L-Di

Pie Chart

A-Di

2-D

R-R R-I R-O R-N I-I N-N

Relational Information Dispalys

3-D 4-D 5-D n-D• • •

A

Table

B CXY nn

yy

nnA

B C

abc

y ny

ny

Matrix

CP-CP-S

CP-CP-S

Dimensionality

Scale Types

Dim

ensi

onal

Rep

rese

nta

tion

s

• • • R-R-R O-O-N• • •

A

B

C

X

Y

ZP-P-T

Network

N-N-N• • •

Example 1: Representation of Altitude

• User analysis– Pilots are the only users of the altimeters in a

cockpit. – Pilots are highly trained domain experts.– Altimeter is one of the many instruments a pilot

uses, especially during takeoff and landing. – High workload and multitasking during takeoff

and landing can significantly affect the pilot’s processing of altitude information.

Example 1: Representation of Altitude

• Functional analysis– The primary function of an altimeter is to

provide altitude information (static or dynamic) to the pilots for the taxing, takeoff, cruising, and landing of an airplane.

Example 1: Representation of Altitude

• Task analysis– Reading the absolute numeric value of an

altitude.– Perceiving the direction of vertical motion.– Perceiving the vertical position of the airplane.– Capturing a specific altitude.– Maintaining a specific altitude..

Example 1: Representation of Altitude

• Representational analysis

10

1

2

3

45

6

7

8

9 10

1

2

3

45

6

7

8

9

12,720

(A) Analog Altimeter (B) Digital Altimeter (C)Tape Altimeter

12800

13000

12600

12500

13200

1 2 7 2 04 0

0 0

Altitudes(Numbers)

1 + 1 D 1 D

Length-Orientation Position-Shape Height Orientation

12,7201 1

Example 1: Representation of Altitude

• Mapping between tasks and representations

Example 2 was removed due to copyright and other concerns

Conclusion

• Visualization is externalization of information

• Externalization can make visualization good or bad

• Correct mapping between task and representation is essential for a good visualization