CHAPTER 15 – TASK ANALYSIS TYLER BRAZELL, MARC SMITH, MEGAN LISTER.
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Transcript of CHAPTER 15 – TASK ANALYSIS TYLER BRAZELL, MARC SMITH, MEGAN LISTER.
CHAPTER 1
5 – TA
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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????