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CMC/CC A Task Analysis. Master IK, CIW, MMI L.M. Bosveld-de Smet Hoorcollege 4; ma. 25 sept. 2006; 16.00-18.00. Goals of system engineering. Adequate functionality What tasks and subtasks must be carried out? Task analysis is central! Reliability Standardization

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cmc cc a task analysis

CMC/CC ATask Analysis

Master IK, CIW, MMI

L.M. Bosveld-de Smet

Hoorcollege 4; ma. 25 sept. 2006; 16.00-18.00

goals of system engineering
Goals of system engineering
  • Adequate functionality
    • What tasks and subtasks must be carried out?
    • Task analysis is central!
  • Reliability
  • Standardization
  • Schedule and budgetary planning
    • Attention to human factors
    • Rigorous testing
process of design in hci
Process of design in HCI
  • Requirements
    • what is wanted?
  • Analysis
    • Task models – means to capture how people carry out tasks
  • Design
    • Modeling and describing interaction
    • Theories, design principles (basic heuristics), guidelines
  • Iteration and prototyping
  • Implementation and deployment
task analysis
Task Analysis
  • Process of analyzing the way people perform their jobs
  • Essential part of Requirements Analysis
  • Essential part of HCI Design
  • Failure may result in serious usability problems
task analysis different approaches
Task Analysis: different approaches
  • Task decomposition
    • Looks at the way a task is split into subtasks, and the order in which these are performed
  • Knowledge-based techniques
    • Look at what users need to know about the objects and actions involved in a task, and how that knowledge is organized
  • Entity-relation-based analysis
    • Object-based approach, where emphasis is on identifying actors and objects, the relationships between them and the actions they perform
task decomposition hta example
Task Decomposition: HTA example

0. In order to clean a house

1. get the vacuum cleaner out

2. fix the appropriate attachment

3. clean the rooms

3.1. clean the hall

3.2. clean the living rooms

3.3. clean the bedrooms

4. empty the dust bag

5. put the vacuum cleaner and attachments away

Plan 0: do 1-2-3-5 in that order; when the dust bag gets full do 4.

Plan 3: do 3.1 every day; do 3.2 once a week; when visitors are due do 3.3

hta making a cup of tea
HTA: making a cup of tea

Plan 0

Do1; at the same time, if the pot is full do2;

Then do 3-4;

After 4 or 5 minutes do 6

0.

make a cup

of tea

1.

Boil water

2.

Empty pot

3.

Put tea leaves

In pot

4.

Pour in boiling

water

5.

Wait 4 or 5

minutes

6.

Pour tea

1.1.

Fill kettle

1.2.

Put kettle on

hob

1.3.

Wait for kettle

to boil

1.4.

Turn off gas

Plan 1

Do 1.1-1.2-1.3

When kettle boils do 1.4

hta for making lots of cups of tea
HTA for making lots of cups of tea

Plan 0

Do1; at the same time, if the pot is full do2;

Then do 3-4;

After 4 or 5 minutes do 5

Plan 1

Do 1.1-1.2-1.3-1.4

When kettle boils do 1.5

0.

make cups

of tea

1.

Boil water

2.

Empty pot

3.

Make pot

4.

Wait 4 or 5

minutes

5.

Pour tea

5.1.

Put milk in

cup

5.2.

Fill cup with

tea

5.3.

Do sugar

Plan 3

3.1-3.2-3.3

3.1.

Warm pot

3.2.

Put tea leaves

in pot

3.3.

Pour in boiling

water

5.3.1.

Ask guest

about sugar

5.3.2.

Add sugar to

taste

Plan 5.3

5.3.1

if wanted 5.3.2

1.1.

Fill kettle

1.2.

Put kettle on

hob

1.3.

Turn on and

light gas

1.4.

Wait for kettle

to boil

1.5.

Turn off gas

hta for making lots of cups of tea1
HTA for making lots of cups of tea

Plan 5 (pour tea)

NO

empty cups ?

for each guest 5.3

5.1

5.2

YES

types of plan
Types of plan
  • Fixed sequence
  • Optional tasks
  • Waiting for events
  • Cycles
  • Time sharing
  • Discretionary
  • Mixtures
knowledge based analysis
Knowledge-based analysis
  • Listing of all objects and actions involved in task
  • Building taxonomies
  • One technique:
    • task analysis for knowledge description (TAKD)
      • Task descriptive hierarchy (TDH)
knowledge based analysis example
Knowledge-based analysis: example

Kitchen item OR

preparation

mixing bowl, plate, chopping board

cooking

frying pan, casserole, saucepan

dining

plate, soup bowl, casserole, glass

knowledge based analysis example takd
Knowledge-based analysis: exampleTAKD

Kitchen item AND

/_ shape XOR

/ |_ dished

/ | mixing bowl, casserole, sauce pan, soup bowl, glass

/ |_ flat

/ plate, chopping board, frying pan

/_ function OR

{_ preparation

{ mixing bowl, plate, chopping board

{_ cooking

{ frying pan, casserole, sauce pan

{_ dining XOR

|_ for food

| plate, soup bowl, casserole

|_ for drink

glass

knowledge based analysis example tdh for actions
Knowledge-based analysis: exampleTDH for actions

Kitchen job OR

|__ preparation

| beating, mixing

|__ cooking

| frying, boiling, baking

|__ dining

pouring, eating, drinking

sources for task analysis
Sources for task analysis
  • Documentation
  • Domain expert opinion
  • Direct observation
task analysis related to interface design
Task analysis related tointerface design
  • Never complete
  • Should not be the sole arbiter of interface style and structure
designing user interfaces
Designing User Interfaces

“Designing user interfaces is a complex and highly creative process that blends intuition, experience, and careful consideration of numerous technical issues”

Ben Shneiderman (1998, 3rd ed.)

user interface
User Interface
  • Locus of interaction
  • Cushioning buffer
  • Visible aspect of the invisible system
design effective interfaces
Design Effective Interfaces

Basic questions:

  • Who is the user?
  • What is the task?
  • What is the environment in which the system will operate?
designer guidance i
Designer Guidance I
  • Measurable human factors
    • time to learn
    • speed of performance
    • rate of errors
    • retention over time
    • subjective satisfaction
  • Often forced tradeoffs
designer guidance ii
Designer Guidance II
  • High-level theories and models
  • Middle-level principles
  • Specific and practical guidelines
high level theories i
High-level theories I
  • Four-level approach of Foley & van Dam (1990): conceptual-semantic-syntactic-lexical
  • GOMS and the keystroke-level model Card, Moran& Newell (1980,1983); Kieras & Polson (1985); Kieras (1988); Elkerton & Palmiter (1991)
high level theories ii
High-level theories II
  • Stages-of-actions models: Norman (1988)’s 7 stages of action
    • forming goal
    • forming intention
    • specifying action
    • executing action
    • perceiving system state
    • interpreting system state
    • evaluating outcome
high level theories iii
High-level theories III
  • Consistency/Completenes through action grammars: Reisner (1981); Payne & Green (1986)
    • task[Direction, Unit] -> symbol[Direction] + letter[Unit]
    • symbol[Direction=forward] -> “CTRL”
    • symbol[Direction=backward] -> “ESC”
    • letter[Unit=word] -> “W”
    • letter[Unit=character] -> “C”
high level theories iv
High-level theories IV
  • Widget-level theories: Object-Action Interface Model of Shneiderman (1980, 1981, 1983)
    • Hierarchies of task objects and actions
    • Hierarchies of interface objects and actions
    • Metaphoric representation conveys interface objects and actions
    • Tuning of interface objects and actions to fit the task
    • Direct manipulation approach to design
    • Minimizing burdens of syntax
understand the user
Understand the user
  • Physical abilities and physical workplaces
  • Cognitive and perceptual abilities
  • Personality differences
  • Cultural and international diversity
  • Users with disabilities
  • Elderly users
the notion of task in hci draper 1993
The Notion of Task in HCIDraper, 1993
  • Problematic notion: a task is not the same thing to all people in all circumstances (e.g. preparing a business letter)
  • Plea in favour of prototyping cycle for task analysis: task analysis -> design product -> build prototype -> evaluate
testing of accomplishments of design goals
Testing of accomplishments of design goals
  • Pilot studies
  • Expert reviews
  • Usability tests
  • Acceptance tests
summary
Summary
  • Task analysis
  • “Know thy user”
  • Recording task objects and actions
  • Construction of suitable interface objects and actions
  • Extensive testing
  • Iterative refinement