CMPUT 301: Lecture 17Usability Paradigms and Principles

Lecturer: Martin JagersandDepartment of Computing Science

University of Alberta

Notes based on previous courses byKen Wong, Eleni Stroulia

Zach Dodds, Martin Jagersand

2

Problems

• Development: How can we ensure the usability of an interactive system as we develop it?

• Evaluation: How can the usability of an interactive system be demonstrated or measured?

3

Solutions

• Two complementary approaches:– paradigms

– see successful examples as inspiration for future development

– principles– derive theories for effective interaction using

knowledge of sensory and perceptual psychology, sociology, and computing

4

Approaches

• Paradigms1. specific

2. technology driven

3. not well defined

4. practical

• Principles1. General (applies whenever

humans interact with each other or machines)

2. technology independent

3. Repeatable

4. Based on theory

5

Paradigms

• Time-sharing:– 40’s and 50’s: increasing computing power – Several users share the computing power of one

central machine– shift from batch to interactive use– provide each user the illusion of a full computer– Unix

[Dennis Ritchie et al. 1969 (Bell Labs)]– VM360,70,90 and CMS (IBM)

6

Paradigms

• Video display units:– 50’s 60’s– Display data as graphics– shift away from tty paper printouts

• Sketchpad [Ivan Sutherland 1962 (MIT)]

– interact with visual objects to modify computer memory.

– Visual-motor manipulation versus coding

7

Paradigms

• Sketchpad:– light pen and 9”

cathode ray tube

– ran on 320 K RAM

– user manipulates geometric shapes

– object-oriented language

– hierarchical structures

– Spatial organization and saliency

8

Paradigms

• Integrated environments:– use computers to enhance human solving of

complex problems. – Assume naive human (revolutionary; at the time only

experts used computers)

– provide the right toolkit by composing the right tools (Carpenter analogy: re-uses tools)

– NLS (oNLine System)[Douglas Englebart 1968 (SRI)]

9

Paradigms

• oN Line System:– mouse, chording keyboard,

high-resolution display

– integrated, configurable, graphical environment

– online word and outline editing

– hypertext linking

– electronic messaging

– video conferencing

10

Paradigms

• Short-sighted:I think there is a world market out there for maybe five computers.— Thomas Watson, chairman of IBM, 1943

There is no reason anyone would want a computer in their home.— Ken Olson,founder of DEC, 1977

Remember: Early days computers were used either for scientific calculations or by governments to keep track of individuals

11

Paradigms

• Visionary:The best way to predict the future is to invent it.— Alan Kay

12

Paradigms

• Personal computing:– computing for everyone

(not just the intellectual elite)

• Papert:– Logo

• Alan Kay 1969 (U Utah)– Vision of Dynabook– Smalltalk

13

Paradigms

• Dynabook:– cardboard prototype

– portable and robust

– touch screen

– wireless

– graphical user interface

– so simple, a child could use it

14

Paradigms

• Xerox PARC:– Smalltalk

– object oriented language and environment

– Ethernet– standard, layered communications protocols

– client/server architecture– decentralized computing

– laser printing– seamlessly transfer digital documents to paper

15

Paradigms

• The metaphor:– use metaphors to teach new concepts

– e.g., desktop metaphor for filing tasks, file, folder.

– Note: precedes graphic desktop interfaces (Windows)

– metaphors can only go so far– e.g., trash can, floppy disks, hard drives, etc.

– non-intuitive situations– e.g., dragging floppy to trash to eject (Mac)

– cultural bias

16

Paradigms

• WIMP user interface:– put user in temporal control over the program– allow humans to switch/resume contexts– contexts are shown in windows

17

Paradigms

• Early WIMP:– Alto

– [Xerox PARC 1970s]

– Star– [Xerox 1981] ($15000)

18

Paradigms

• Early WIMP:– Lisa

– [Apple, 1983]($10000)

– Macintosh– [Apple, 1984]

($2500)

19

Paradigms

• Direct manipulation: (Schneiderman ’82)– visibility of the objects of interest

– i.e., recognition, not recall

– incremental action with rapid feedback– e.g., rubberbanding

– reversible actions (undo)– i.e., encourage safe exploration

– every choosable action is legal– e.g., graying out invalid choices

– manipulation of objects directly– i.e., instead of command line

– Needs high bandwidth interaction with human.

20

Paradigms

• WYSIWYG:– what you see is what you get– minimize the difference between onscreen

presentation and final printed product– not a panacea for usability– versus markup languages?

• Related to direct manipulation

21

Paradigms

• Language versus action:– complicated, repetitive tasks are often tedious to do

via direct manipulation– e.g., renaming the suffix of a group of files

– use a scripting language as a kind of intermediary between the user and system

– i.e., programmable, recordable, attachable

– e.g., program by example

22

Paradigms

• Hypertext:– authoring, navigating, and reading linked, non-

linear information– Memex proposal [Vannevar Bush 1945]

“As We May Think”– hypertext

[Ted Nelson 1965 (Harvard U)]

23

Paradigms

• Memex:– an information storage

and retrieval “desk”

– linking, indexing, annotation, trails

– enhance human memory and associative capacity

24

Paradigms

• Multi-modality:– use multiple human communication channels– combine visual, audio, and haptic channels (in

better ways than through keyboard and VDU. Note that as humans we are always multimodal)

– e.g., sound effects, notification, force feedback

25

Paradigms

• CSCW:– computer supported cooperative work– network computers together to support human

collaboration– asynchronous or synchronous– e.g., email, videoconferencing

26

Paradigms

• The World Wide Web:– merging of hypertext, networking, and personal

computing– Internet

[1969 (DARPA et al.)]– WWW

[Tim Berners-Lee 1989 (CERN)]– Mosaic web browser

[Marc Andreesen 1993 (NCSA)]

27

Paradigms

• Agent-based interfaces:– software agents act on the behalf of users– More than a direct command -> action mapping– e.g., email filtering agents, web crawlers

28

Paradigms

• Ubiquitous computing:– computers are everywhere,

but become no longer noticeable– electric motor analogy– utility ubiquity invisibility– special devices versus general devices– ubiquitous computing

[Mark Weiser 1991 (Xerox PARC)]

29

Paradigms

• Scales of computing:– yard-sized

– e.g., SMART Board

– foot-sized– e.g., tablet computer

– inch-sized– e.g., Palm Pilot,

electronic Post-Its?

30

Paradigms

• Future?:– emerging technologies

– wireless networking

– voice recognition

– pen-based computing

– wearable computing

– vision systems

– biometrics

– etc.

31

Paradigms

• Future?:– moving from the traditional desktop to a

“smart” environment– interacting in multiple modes: keyboard, voice,

gesture, etc.

32

End

• What did I learn today?

• What questions do I still have?