CMPUT 301: Lecture 15 Task Analysis Lecturer: Martin Jagersand Department of Computing Science University of Alberta Notes based on previous courses by Ken Wong, Eleni Stroulia Zach Dodds, Martin Jagersand

2 Today: Some notes on the main course project. Hierarchical task analysis Temporal execution plans Knowledge based analysis

3 Task Analysis Process of analyzing the way people perform their jobs: –the things they do –the things they act on –the things they need to know Focuses on observable aspects of a task (as opposed to internal cognitive states)

4 Goal: For Computer Science: 1.To understand how people solve tasks 2.To be able to map parts of this work effectively into a computer program (which people still usually interact with) But nothing new under the sun: Consider how early capitalist theory (e.g. Adam Smith) and industrialists (e.g. Henry Ford) subdivided and analyzed factory work to increase economic gain

5 Task Analysis To clean the house: –get the vacuum cleaner out –attach the appropriate tool –clean the rooms –when the dust bag gets full, replace it –put the vacuum cleaner and tools away

6 Task Analysis To vacuum, need to know about: –vacuum cleaners –tool attachments –dust bags –storage closet –rooms to be cleaned –etc.

7 Task Analysis Three approaches: –task decomposition (hierarchical and temporal) –look at splitting a task into subtasks and the order in which these are performed –knowledge-based analysis –look at what users need to know about objects and actions involved in a task –entity-relation-based techniques –look at identifying the actors and objects, the relationships between them, and the actions performed

8 Task Analysis Purpose: –for new systems, helps in capturing and deriving the requirements, prior to design –for existing systems, helps in clarifying knowledge about the current situation Issues: –may include non-computer activities –focus on observable user behavior

9 Task Decomposition Hierarchical task analysis (HTA): 1.produce a hierarchy of tasks and subtasks 2.produce temporal plans to describe ordering of (sub)tasks and conditions under which they occur

10 HTA Task Decomposition 0 To clean the house: –1 get the vacuum cleaner out –2 attach the appropriate tool –3 clean the rooms –3.1 clean the hall –3.2 clean the living room –3.3 clean the bedrooms –4 empty the dust bag –5 put the vacuum cleaner and tools away

11 HTA Task Decomposition Possible temporal plans for tasks and subtasks: –plan 0 –do 1, 2, 3, 5 in that order –when the dust bag gets full, do 4 –plan 3: –do any of the rooms 3.1, 3.2, or 3.3 in any order depending on which rooms need cleaning

12 Task Decomposition Temporal refinements: –plan 3 –do 3.1 every day –do 3.2 once a week –do 3.3 when visitors are coming

13 Task Decomposition When to stop decomposing subtasks? Example: Computer assisted training system: –P x C < threshold –P = probability of making a mistake –C = cost of the mistake –depends on intended purpose and audience

14 Task Decomposition Other stopping rules: 1.When human is too complex to model: –when the task contains complex motor responses (human sensory motor) –when the task involves internal decision making (human cognitive) 2.Benefit analysis of time, economic return etc.

15 Task Decomposition: Add sequential and temporal info

16 Task Decomposition: Refine and add iteration Note: loop!

17 Temporal Task Decomposition Types of plans: –fixed sequence –e.g., make pot –optional tasks –e.g., empty pot –waiting for events –e.g., when kettle boils –cycles –e.g., pour tea –time-sharing –e.g., boil water and empty pot –discretionary –combinations

18 Knowledge-Based Analysis Understand the knowledge needed to perform a task: –list all objects and actions involved –build taxonomies to structure these –use this understanding for training

19 Knowledge-Based Analysis Need to know about: car control classification –steering  steering wheel, indicators –engine/speed –direct  ignition, accelerator, foot brake –gearing  clutch, gear stick –lights –external  headlights, hazard lights –internal  courtesy light –parking  hand brake, door lock –etc.

20 Knowledge-Based Analysis Taxonomy: –different structures might be possible, depending on intended purpose and audience –e.g., –driving versus repairing by mechanic

21 Knowledge-Based Analysis Task descriptive hierarchy: –XOR | –object in only one category –AND / –object in all categories –OR { –object in at least one category

22 Knowledge-Based Analysis car controls XOR –… –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 –…

23 Knowledge-Based Analysis kitchen item OR –preparation  mixing bowl, plate, chopping board –cooking  frying pan, casserole, saucepan –dining  plate, soup bowl, casserole, glass

24 Knowledge-Based Analysis Uniqueness rule: –must be able to distinguish any two specific objects –e.g., –cannot distinguish mixing bowl and chopping board –can distinguish mixing bowl and plate

25 Knowledge-Based Analysis kitchen item AND –/ shape XOR –| dished  mixing bowl, casserole, saucepan, soup bowl, glass –| flat  plate, chopping board, frying pan –/ function OR –…

26 Knowledge-Based Analysis kitchen item AND –/ shape XOR –… –/ function OR –{ preparation  mixing bowl, plate, chopping board –{ cooking  frying pan, casserole, saucepan –{ dining XOR –| for food  plate, soup bowl, casserole –| for drink  glass

27 Knowledge-Based Analysis Unique path: –each object can be represented by a knowledge representation grammar (KRG) term –e.g., –a casserole dish –kitchen item/shape(dished)/ function{cooking,dining(for food)}/ –kitchen item whose shape is dished AND its function is cooking OR dining for food

28 Knowledge-Based Analysis Taxonomy of actions: –can also structure actions, based on genericity instead of a “how to do it” decomposition –make general statements about tasks

29 Knowledge-Based Analysis kitchen job OR –{ preparation  beating, mixing, pouring –{ cooking  frying, boiling, baking –{ dining  pouring, eating, drinking

30 Knowledge-Based Analysis Taxonomies of objects and actions –crosscheck to look for omissions –perhaps easier to see what people use than to see what they do –add taxonomies –e.g., classify foods

31 Knowledge-Based Analysis Generic descriptions of simple tasks: –KRG sentence –e.g., –eating a carrot off a plate –kitchen job(dining) using a kitchen item /shape(flat)/function{dining,preparation}/ to food(root vegetable)

32 Knowledge-Based Analysis Issues: –generification –not bothering with certain low-level distinctions –too many different KRG sentences –perhaps more generification needed –too few different KRG sentences –level of abstraction too great

33 End What did I learn today? What questions do I still have?