1. Professor John Canny Fall 2001 Sept 11, 2001
CS 160: Lecture 5
Professor John Canny
Fall 2001
Sept 11, 2001
12/8/2018

2. Administrivia You’re in a project group now (see the web site)
Make sure you meet this week and come up with a project proposal.
Hand in the proposal by Friday 5pm.
Ask the audience what is wrong with this!
12/8/2018

3. Task Analysis A technique for analyzing existing tasks by observation.
Doesn’t require understanding of Users’ goals, just what they do.
But because of that its harder to apply to the design of a new system.
Good for training materials and documentation
Ask the audience what is wrong with this!
12/8/2018

4. Task Analysis: 3 Approaches
Tasks decomposition: looks at how a task is split into subtasks and the order in which these are performed.
Knowledge-based techniques: what do users need to know about the objects and actions involved in a task? How is that knowledge organized?
Entity-relation-based analysis: an object-based approach, identify objects, relationships and actions.
Ask the audience what is wrong with this!
12/8/2018

5. Task Decomposition Break the task into subtasks:
Hierarchical Task Analysis (HTA):
Organize tasks into a hierarchy
Include ordering constraints
Looks something like logic programming (PROLOG)
Clean house
Ask the audience what is wrong with this!
Get vacuum cleaner
Clean rooms
Empty dustbag
Put everything away
Clean hall
Clean living room
Clean bedrooms
12/8/2018

6. Task Decomposition 0. In order to clean house Get vacuum cleaner out
Fix attachment
Clean the rooms
3.1 Clean the hall
3.2 Clean the living rooms
3.3 Clean the bedrooms
Empty the dustbag
Put the vacuum cleaner away
Plan 0: Do in that order
Plan 3: Do any of 3.1, 3.2, and 3.3 in any order depending on which rooms need cleaning
Ask the audience what is wrong with this!
12/8/2018

7. Task Decomposition Real tasks have more structure:
Possible ordering of steps
Frequency of steps
Task achievement (all or some subtasks)
Ask the audience what is wrong with this!
12/8/2018

8. Stopping Conditions P x C rule:
P is probability of a user error on the subtask
C is the cost of the error
When P x C is small enough, we stop expanding
Can also stop at “skill” steps, where the users actions are not reflective (conscious)
Ask the audience what is wrong with this!
12/8/2018

9. Task Variations Optional tasks Waiting for Events Cycles Time-sharing
Ask the audience what is wrong with this!
12/8/2018

10. Aside: situated action
Not all activities fit the task decomposition hierarchy nicely
Think about tidying a room (vs. cleaning)
See an item, put it away
Look at the arrangement of things, change it
The arrangement of things suggests classifications...
Your behavior is heavily influenced by the environment
So don’t forget to observe real behavior when doing task analysis
Ask the audience what is wrong with this!
12/8/2018

11. Knowledge-based analysis
Basic idea: start with list of items, then organize into a taxonomy (often ends up being a hierarchy)
e.g. driving:
Steering wheel
Seat belt
Horn control
Seats
Windscreen
Speedometer
Dashboard
Steering column
Foot pedals...
Ask the audience what is wrong with this!
12/8/2018

12. Knowledge-based analysis
Controls:
Steering wheel
Horn control
Speedometer
Foot pedals…
Structural
Seats
Seat belt
Dashboard
Steering column
Windscreen
Ask the audience what is wrong with this!
12/8/2018

13. Knowledge-based analysis
Controls:
Steering wheel
Horn control
Speedometer
Foot pedals…
Structural
Seats
Seat belt
Dashboard
Steering column
Windscreen
Ask the audience what is wrong with this!
12/8/2018

14. Producing a taxonomy Start with an exhaustive list
Using existing taxonomies (e.g. parts catalog)
Put the items on cards - have users arrange them
Taxonomies can be captured with attribute - value pairs, some required, some optional
TAKD (Task Analysis for Knowledge Description) produces a Task Descriptive Hierarchy (TDH)..
Ask the audience what is wrong with this!
12/8/2018

15. TDH
Conjunctives:
wash/wipe AND function XOR wipe front wipers, rear wipers wash front washers, rear washers position XOR front front wipers, front washers rear rear wipers, rear washers
Ask the audience what is wrong with this!
12/8/2018

16. More on TDH TDH can be applied to actions as well as objects.
In comparison with HTA (Hierarchical Task Analysis), TDH Focuses on similarity of objects
HTA groups objects which are related by the task
HTA allows arbitrary repetition, TDH encourages uniqueness.
Ask the audience what is wrong with this!
12/8/2018

17. KRG
Once we have a TDH, we can describe tasks in quasi-english sentences, using the TDH terms as standard nouns and verbs.
Idea is to describe the task at the right level of abstraction, with unambiguous terms.
Sounds a lot like XML...
Ask the audience what is wrong with this!
12/8/2018

18. Entity-relationship techniques
Borrowed from OO databases
Objects
Concrete Objects
Actors
Composite Objects
Actions
Have at least a “patient” X (action is done to X)
Often an “agent” (who does the action)
May involve other objects “instruments”
(agent) Sam planted the leeks (patient) with his spade (instrument)
Ask the audience what is wrong with this!
12/8/2018

19. Objects
Objects
Concrete Objects
Actors
Composite Objects
Composite objects are collections of objects “the team”, “the kit” - sets of things
Composite objects may also be “tuples”, e.g. an office comprises desks, chairs, file cabinets...
Ask the audience what is wrong with this!
12/8/2018

20. Actions-messages
Messages are a very important kind of action because they often influence other actions
People ask people to do things
People commit to doing things
We acknowledge completion of actions
Speech-act theory studies this
Ask the audience what is wrong with this!
12/8/2018

21. Entities and relationships
Object Sam Actions: S1: drive tractor S2: dig carrots
Relations: object-object
location(pump3, glasshouse)
Relations: action-event before(plant seed, germinate) triggers(water seed, germinates seed)
Ask the audience what is wrong with this!
12/8/2018

22. Sources of information
Existing documentation
Observation in a worked example
Interviews (create specific scenarios)
Ask the audience what is wrong with this!
12/8/2018

23. Uses of task analysis Manuals and documentation
Requirements capture for design
Detailed UI design
Ask the audience what is wrong with this!
12/8/2018

24. Summary Find your group members!
Project proposals due Friday (JFC’s office mailbox)
Task analysis is a way to understand work
There are 3 different ways of approaching it (which can be used together to some extent)
Ask the audience what is wrong with this!
12/8/2018