CHAPTER 1

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ANALYSIS

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INTRODUCTION

What is task analysis?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 out2. Fix the attachment3. Clean the rooms4. When the dust bag gets full, empty it5. Put the vacuum cleaner and tools away

DIFFERENCES BETWEEN TASK ANALYSIS AND OTHER TECHNIQUES

Systems analysis vs. Task analysis

system design - focus - the user

Cognitive models vs. Task analysis

internal mental state - focus - external actions

practiced ‘unit’ task - focus - whole job

THREE APPROACHES TO TASK ANALYSIS

Task decomposition:Which looks at the way a task is split into subtasks, and the order in

which these are preformed

Knowledge-based 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: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.

TASK DECOMPOSITION

Most task analysis techniques involve some form of task decomposition to express this sort of behavior.

Aims:describe the actions people dostructure them within task subtask hierarchydescribe order of subtasks

Variants: Hierarchical Task Analysis (HTA)

most common Collaborative Task Tree (CTT) (CNUCE, Pisa)

uses LOTOS temporal operators

TEXTBOOK EXAMPLEHierarchy 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. When 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 list of tasks

2 . Group tasks into higher level tasks

3 . Decompose lowest level tasks further

How do we know when to stop?

Is “empty the dust bag” simple enough?Purpose: expand only

relevant tasksMotor actions: lowest

sensible level

P x C RuleSays 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 cleanerfix carpet headclean dinning roomclean main bedroomempty dustbagclean sitting roomput 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 talked about, here is a video of how to use hierarchal task analysis to set a table.

HTA EXAMPLE

TYPES OF PLANS

fixed sequence - 1.1 then 1.2 then 1.3

optional tasks - if the pot is full 2

wait for events - when kettle boils 1.4

cycles - do 5.1 5.2 while there are still empty cups

time-sharing - do 1; at the same time ...

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.

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 common knowledge between tasks.

Class Participation: What would be considered an example of an everyday taxonomy?

KNOWLEDGE-BASED ANALYSIS EXAMPLEmotor controls

steering steering wheel, indicators

engine/speed

direct ignition, accelerator, foot brake

gearing clutch, gear stick

lights

external headlights, hazard lights

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

radio numerous!

TASK DESCRIPTION HIERARCHY (TDH)

Three types of branch point in taxonomy: 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 descriptions of tasksThat 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

Start with list of objects and classify them:

Concrete objects (specifies):simple things: spade, plough, glasshouse

Actors:human actors: Vera, Sam, Tony, the customers

Composite objects (abstract):sets: the team = Vera, Sam, Tonytuples: tractor may be < Fergie (the tractor), plough >

ATTRIBUTES

To the objects, add attributes:

Example: Irrigation PumpAttributes:

status: on/off/faultycapacity: 100 litres/minute

Example: TVsAttributes:

Status: On/Off/Stand ByType: Low Def./ High Def./Smart TV

ACTIONS

Actions change the patient (the state of something)

Performed by the agent (someone or something)

There can be other attributes associated with an actionThese are known as instruments

Example: “the gardener dug the soil with the spade”Patient: SoilAgent: GardenerInstrument: Spade

EVENTS

Anything which happensActions performed are always eventsCan 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 allExample: Temperature changes

Events are also timedExample: “At midnight”

RELATIONSHIPS

Tie objects, actions, and events together

Object-ObjectIrrigation pump 3 is situated in the glasshouse

Action-ObjectVera tells Sam to dig the carrots with the spade

ATOM METHOD

Analysis for Task Object Modeling (ATOM)Can be done in two ways

Analyze the order of subtasks and actions annotated by the objects involvedRefer to page 529

Can produce for any particular object a “life cycle” diagram representing all the actions in which it participatesRefer to page 530

Most methods include some notion of class or inheritance hierarchy

SOURCES OF INFORMATION AND DATA COLLECTION Documentation

Observation

Interviews

Initial Analysis

Sorting and Classification

USES OF TASK ANALYSIS

Manuals and Tuition

Requirements Capture and Systems Design

Detailed Interface Deisgn

SUMMARY

There are several task analysis Hierarchical task analysis decomposes a task into subtasksCan be recorded either in a textual outline format or in a tree

diagramKnowledge 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

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: http://www.hcibook.com/e3/scenario/phone

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.

OUR ANSWER- QUESTION 1

OUR ANSWER (CONT.) – QUESTION 2 & 3

THE END

Any Questions????