CMC/CC A Task Analysis Master IK, CIW, MMI L.M. Bosveld-de Smet Hoorcollege 4; ma. 25 sept. 2006; 16.00-18.00.

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 Schedule and budgetary planning

Attention to human factors Rigorous testing

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

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 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

0. In order to clean a house1. get the vacuum cleaner out2. fix the appropriate attachment3. clean the rooms

3.1. clean the hall3.2. clean the living rooms3.3. clean the bedrooms

4. empty the dust bag5. 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

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 0

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

Then do 3-4;

After 4 or 5 minutes do 6

Plan 1

Do 1.1-1.2-1.3

When kettle boils do 1.4

HTA for making lots of cups of tea

0. make cups

of tea

1. Boil water

2. Empty pot

3. Make pot

3.3. Pour in boiling

water

4. Wait 4 or 5 minutes

5. Pour tea

1.1. Fill kettle

1.2. Put kettle on

hob

1.4. Wait for kettle

to boil

1.5. Turn off gas

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

1.3. Turn on and

light gas

3.2. Put tea leaves

in pot

3.1. Warm pot

5.3.1. Ask guest

about sugar

5.3.2. Add sugar to

taste

5.1. Put milk in

cup

5.2.Fill cup with

tea

5.3. Do sugarPlan 3

3.1-3.2-3.3

Plan 5.3

5.3.1

if wanted 5.3.2

HTA for making lots of cups of tea

Plan 5 (pour tea)

5.1 5.2for each guest 5.3

empty cups ?

NO

YES

Types of plan

Fixed sequence Optional tasks Waiting for events Cycles Time sharing Discretionary Mixtures

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

Kitchen item OR

preparationmixing bowl, plate, chopping board

cookingfrying pan, casserole, saucepan

diningplate, soup bowl, casserole, glass

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: exampleTDH for actions

Kitchen job OR

|__ preparation

| beating, mixing

|__ cooking

| frying, boiling, baking

|__ dining

pouring, eating, drinking

Sources for task analysis

Documentation Domain expert opinion Direct observation

Task analysis related tointerface design

Never complete Should not be the sole arbiter of interface

style and structure

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

Locus of interaction

Cushioning buffer

Visible aspect of the invisible system

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

Measurable human factors time to learn speed of performance rate of errors retention over time subjective satisfaction

Often forced tradeoffs

Designer Guidance II

High-level theories and models

Middle-level principles

Specific and practical guidelines

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

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

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

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

OAI model

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 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

Pilot studies Expert reviews Usability tests Acceptance tests

Summary

Task analysis “Know thy user” Recording task objects and actions Construction of suitable interface objects and

actions Extensive testing Iterative refinement