Task Analysis

1
Task Analysis

• Organizing and understanding activities

2
Agenda

• Hierarchical TA
• Knowledge-based TA
• Entity-relationship TA

3
Task analysis

• Process of analyzing and documenting how people
  perform their jobs or tasks
• Describing how people do their work
• activities
• artifacts
• relations

4
Goals of task analysis

• What actions do people take in a task?
• What objects do people use to do a task?
• What are the relationships between people,
  objects, and actions?
• What do people need to know to do the task?

5
Different techniques

• Task decomposition/hierarchical task analysis
• Knowledge-based / taxonomic
• Entity-relationship

6
Sources

• Documentation
• Observation / interviews
• Participative exercises

7
Uses

• System analysis / requirements
• Instructional manuals (users guide)
• Menu design

8
Task decomposition

• HTA Hierarchical Task Analysis
• Breakdown list all subtasks, divide subtasks
  further if necessary
• Plan specify the order of subtasks for each
  supertask
• Graphical diagrams to make HTAs clearer

9
Lets try one
10
Tea anyone?

• 0. make cups of tea
• 1. boil water
• 1.1 fill kettle
• 1.2 put kettle on hob
• 1.3 wait for kettle to boil
• 1.4 turn off gas
• 2. empty pot
• 3. put tea leaves in pot
• 4. pour in boiling water
• 5. wait 4 or 5 minutes
• 6. pour tea

plan 0. do 1 at the same time, if the pot is full
2 then 3-4 after four or five minutes do 6 plan
1. 1.1 1.2 1.3 when kettle boils 1.4
11
Tea anyone?

• Graphical diagram

plan 0. do 1 at the same time, if the pot is full
2 then 3-4 after four or five minutes do 6
plan 1. 1.1 1.2 1.3 when kettle boils 1.4
12
Using HTA for analysis

• Properties of the decomposition
• imbalanced
• complicated plans

13
HTA granularity

• Tasks can be indefinitely subdivided
• E.g. Type hello ? Type h ? Press a key ?
  lift finger ? etc.
• How do we know when to stop?

14
Elements of HTA plans

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

15
Knowledge-based

• TAKD Task Analysis for Knowledge Description
• Taxonomic (unique categorizations of items and
  actions)
• Emphasizes the similarities between objects and
  functions
• Good for menu design understanding problem
  language

16
TAKD

• Focused on categorizing objects by action,
  function, or other properties
• List all objects and actions associated with the
  task
• Build taxonomy using AND, OR, and XOR branching

17
Try one?
18
Kitchen items

• kitchen item AND
• /______ shape XOR
• / _____________ dished
• / mixing bowl, casserole, sauce pan, glass
• / _____________ flat
• / plate, chopping board, pan
• /______ function OR
• ______ preparation
• mixing bowl, plate, chopping board
• ______ cooking
• frying pan, casserole, saucepan
• ______ dining
• ______ for food
• plate, soup bowl, casserole
• ______ for drink
• glass

19
Entity-Relationship

• Similar to OO design
• Identify object-action relations

20
Entity-Relationship

• Identify objects concrete objects, actors,
  composite objects
• Classify objects and list relevant attributes
• Associate actions with objects
• Identify events and relations

21
Example!
22
Market gardening firm

• Object Sam human actor the proprietor
• Actions as worker
• S1 plant marrow seed
• S2 program irrigation controller
• Actions as manager
• S3 tell Vera to dig the carrots
• Object the team composite
• Comprises Sam, Vera
• Object glasshouse simple
• Attribute
• humidity 0-100
• Object Irrigation Controller non-human actor
• Actions
• IC1 turn on Pump1
• IC2 turn on Pump2
• IC3 turn on Pump3

23
Events relationships

• Object Marrow simple
• Actions
• M1 germinate
• M2 grow
• Events
• Ev1 humidity drops below 25
• Ev2 midnight
• Relations object-object
• location (Pump3, glasshouse)
• Relations action-object
• patient (V2, the carrots)
• - Vera digs the carrots
• Relations action-event
• before (S1, M1)
• - marrow must be sown before it can germinate
• triggers (Ev1, IC3)
• - when humidity drops below 25, controller
  turns on pump 3

24
Task analysis in project

• Must perform one formal task analysis
• How to choose?

25
When to use which?

• Task decomposition
• When sequences are important, ordered processes
• Knowledge-based
• When dealing with many objects, possibly with
  multiple functions, in an environment
• Entity-relationship
• Many actors and objects with many possible
  interactions between

26
Upcoming

• Human capabilities
• Fitts Law predictive modeling
• DFAB 1.1-1.3, Fitts Law paper