# Chapter 15 – Task Analysis - USC Upstate: Faculty

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18 Νοε 2013 (πριν από 4 χρόνια και 5 μήνες)

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INTRODUCTION

Is the process of analyzing the way people preform the jobs: the things they do ,
the things, they act on, and the things they need to know.

Example:

In order to clean the house:

1.
Get the vacuum cleaner out

2.
Fix the attachment

3.
Clean the rooms

4.
When the dust bag gets full, empty it

5.
Put the vacuum cleaner and tools away

OTHER TECHNIQUES

analysis

system design
-

focus
-

the
user

analysis

internal
mental
state
-

focus
-

external actions

-

focus
-

whole job

¾
Which looks at the way a task is split into subtasks, and the order in which these
are preformed

Knowledge
-
b
ased techniques:

Which look at what the users need to know about the objects and actions
involved in a task and how that knowledge is organized

Entity
-
relation
-
based analysis:

¾
Which is an object
-
based approach where the emphasis is on identifying the
actors and objects, the relationships between them and the actions they
preform.

Most task analysis techniques involve some
f
express this sort of behavior.

Aims:

describe
the actions people
do

structure

hierarchy

describe
order of

Variants:

Hierarchical
HTA)

most
common

(CNUCE,
Pisa)

uses
LOTOS temporal operators

TEXTBOOK EXAMPLE

Hierarchy description ...

0
. in order to clean the house

1. get the vacuum cleaner out

2. get 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 vacuum cleaner and attachments away

... and plans

Plan 0: do 1
-

2
-

3
-

5 in that order.

W
hen
the dust bag gets full do
4.

Plan 3: do any of 3.1, 3.2 or 3.3 in any order depending

on which rooms need cleaning

N.B. only the plans denote order

HOW TO GENERATE A HIERARCHY

1. Get

2
. Group

3
. Decompose

How
do we know
when to
stop?

Is
“empty the dust bag”
simple
enough?

Purpose
: expand only
relevant

Motor
actions: lowest
sensible level

P x C Rule

Says that the probability of
making a mistake in the
task is (p) times the cost of
the mistake (
C
) is below a
threshold, then stop
expanding.

STOPPING RULES

HTA PARSING
SCENARIO

get out cleaner

clean dinning room

clean main bedroom

empty
dustbag

clean sitting room

put cleaner away

1.

2.

3.2.

3.3.

3.2.

3.

4.

5.

0.

0. in order to clean the house

1. get the vacuum cleaner out

2. get 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 vacuum cleaner and attachments away

To better explain
what is being
here is a video of
how to use
analysis to set a
table.

HTA EXAMPLE

TYPES OF PLANS

fixed sequence

-

1.1 then 1.2 then 1.3

¾

-

if the pot is full 2

¾
wait for events

-

when kettle boils 1.4

¾
cycles

-

do 5.1 5.2 while there are still empty cups

¾
time
-
sharing

-

do 1; at the same time ...

¾
discretionary

-

do any of 3.1, 3.2 or 3.3 in any order

mixtures

-

most plans involve several of the above

KNOWLEDGE

BASED ANALYSIS

Begins by listing all the objects and actions involved in the task and then building
taxonomies (think about descriptions in biology) of them.

¾
The aim is to understand the knowledge needed to preform a task and thus to
help in the production of teaching materials and in assessing the amount of

¾
Class Participation:

¾
What would be considered an example of an everyday taxonomy?

KNOWLEDGE
-
BASED ANALYSIS EXAMPLE

motor controls

steering
steering

wheel, indicators

engine/speed

direct
ignition, accelerator, foot brake

gearing
clutch, gear stick

lights

external

internal
courtesy light

wash/wipe

wipers
front wipers, rear wipers

washers
front washers, rear washers

heating
temperature control, air direction,

fan, rear screen heater

parking
hand brake, door lock

numerous!

HIERARCHY (TDH)

Three types of branch point in taxonomy:

¾
XOR

normal taxonomy

object
in one and only one
branch

AND

object must be in both

multiple
classifications

OR

weakest case

can
be in one, many or none

ANOTHER TDH EXAMPLE

kitchen item AND

/____shape XOR

/ |____dished mixing bowl, casserole, saucepan,

/ | soup bowl, glass

/ |____flat plate, chopping board, frying pan

/____function OR

{____preparation mixing bowl, plate, chopping board

{____cooking frying pan, casserole, saucepan

{____dining XOR

|____for food plate, soup bowl, casserole

|____for drink
glass

NOTE:
‘/|{’ used for branch types.

ABSTRACTIONS AND CUTS

After producing detailed
taxonomy, we can use these in order to produce generic

¾
That
is, ‘cut’ to yield abstract view

This
is
Knowledge Representation Grammar (KRG
)

KRG terms opt for a generic description or generification.

One example is to break down a tree and make note to how many times a
specific word is mentioned or used. If the number of occurrences is low,
then one does not bother with the lower
-
level distinctions.

The choice of an appropriate level to “cut” the tree is also influence by the
number of different sentences we get for a task.

If there are many, many sentences, we need to use generification.

Although if there are too few sentences, the level of abstraction is too great and
needs to be revaluated.

Entity

relationship
modeling
is an
analysis
technique usually
associated with
database design
and more recently
object
-
oriented
programming.

ENTITY

RELATIONSHIP

BASED TECHNIQUES

OBJECTS

¾
Concrete
objects (specifies):

simple

Actors:

human
actors
:
Vera, Sam, Tony, the customers

Composite
objects (abstract):

sets
:
the team = Vera, Sam,
Tony

tuples
:
tractor may be <
Fergie

(the tractor),
plough >

ATTRIBUTES

To the
objects,

¾
Example:
I
rrigation
P
ump

Attributes:

status
: on/off/faulty

capacity
: 100
litres/minute

Example: TVs

Attributes:

Status: On/Off/Stand By

Type: Low Def./ High Def./Smart TV

ACTIONS

Actions change the patient (the state of something)

¾
Performed by the agent (someone or something)

¾
There can be other attributes associated with an action

¾
These are known as instruments

Example: “the gardener dug the soil with the spade”

¾
Patient: Soil

Agent: Gardener

EVENTS

Anything which happens

¾
Actions performed are always events

Can also encounter spontaneous events

Example: The germination of a marrow seed

No agent is performing the germination

Some spontaneous events have no associated object at all

Example: Temperature changes

Events are also timed

Example: “At midnight”

RELATIONSHIPS

Tie objects, actions, and events together

¾
Object
-
Object

¾
Irrigation pump 3 is situated in the glasshouse

Action
-
Object

¾
Vera tells Sam to dig the carrots with the spade

ATOM METHOD

Analysis for Task Object Modeling (ATOM)

¾
Can be done in two ways

Analyze the order of subtasks and actions annotated by the objects involved

Refer to page 529

Can produce for any particular object a “life cycle” diagram representing all
the actions in which it participates

Refer to page 530

Most methods include some notion of class or inheritance hierarchy

SOURCES OF INFORMATION AND DATA
COLLECTION

Documentation

¾
Observation

¾
Interviews

¾
Initial Analysis

¾
Sorting and Classification

Manuals and Tuition

¾
Requirements Capture and Systems Design

¾
Detailed Interface
Deisgn

SUMMARY

¾

Can be recorded either in a textual outline format or in a tree diagram

Knowledge based techniques built taxonomies of the objects used during a task
and the actions performed upon them

Information for task analysis can be drawn from different sources

¾
Analysis can be used to train and provide instruction

EXERCISE 15.6

This exercise is based on the mobile phone exercise on the book
site:
www.hcibooks.com

A user interface designer analyzes Andy’s behavior with his original
phone and realizes that both scenarios A and B are part of a general
pattern, as shown in the hierarchical task analysis (HTA) in Figure
15.8.

1.
Complete the HTA for phoning using the original phone taking
into account scenarios A and B only briefly describe your
solution.

2.
Do a complete HTA for phoning using the new phone based on
scenario C.

3.
You will find that scenario C does not quiet fit into the general
pattern in Figure 15.8. Discuss whether the solutions to 1 and 2
can be modified to emphasize their common features and
whether this would clarify the over task description.