Chapter 8 : Phase II : Control Task Analysis

1
Chapter 8 Phase II Control Task Analysis

• ? ? ?

2
Contents

• Purpose
• Different approaches to analyzing control tasks
• What is control task analysis?
• The traditional information-processing approach
• What descriptive studies show Expert performance
• An alternative approach Expertise as an active,
  constructive process
• Implications for control task analysis
• Decision ladder
• Basic structure
• Relationship between the decision ladder and the
  abstraction-decomposition space
• Multiple uses of the decision ladder Some
  examples
• Control task analysis for process control
  microworld
• Operating modes
• Set-up
• Discussion Highlighting the key points
• Summary and implications

3
Purpose

• CWA (Cognitive Work Analysis)? ? ?? ??
• To Identify the requirements associated with
  known, recurring classes of situations.
• To identify the constraints on what needs to be
  done, independently of how or by whom
• DURESS II Process control case study
• Modeling tool decision ladder
• CTA? WDA??? ????

4
Different approaches to analyzing control tasks

• Chapter 3 (three types of task analysis
  approaches)
• Input-output (Constraint-based analysis) For
  complex sociotechnical systems
• Sequential flow (Instruction-based analysis)
• Timeline (Instruction-based analysis)
• Additional considerations (TA?? ??? ??)
• To identify the requirements that are associated
  with expert action
• Expert? ???? information systems

5
What is control task analysis? (Control task
analysis? ??? ??)

• CTA? ??? ????, WDA? ??? ??? ????
• CT? WD? ?? (Input-output of CT)
• Control task? Work domain ??? ?? ??? ??? ? (INPUT
  side).
• Control task? Work Domain ??? ?? (OUTPUT side)
• Work Domain Analysis? task, event goal? ??????,
  ?? WDA? ??? ??? ??? Goal? ??
• ??? ?? ???? Goal (beach ?? ??? ??)
• Goal? ???? ???? Work Domain? ??? ?? (??? ?? ?? ??
  ? ?)
• ? class? ??? requirement? ???? ?.
• ?????, ?? ????? ??? event class? ??? requirement?
  ???? ?? Control task analysis.
• Noun? ?? ??? verb? ?? ??? (WD ? CT)

6
Control task ? Work domain? ??
Control Tasks
Act-on
Information-to
Work Domain
7
What is control task analysis? (Control task
analysis? ??? ??)

• CTA describes only what needs to be done, not how
  or whom
• How tasks can be done (?? ?? ??)
• How should be allocated to different actors (??
  ?? ??)
• ?, ??? ???? ??, allocate?? ? ?? ?? ?
• Open System (complex socio-technical systems)
• They require context-conditioned variability to
  adapt to disturbances
• ?? ??? ?? ???? ?? ???? ?? ????? ?
• ??? Requisite variability? ????? ??
  Input-output??? ???.
• Input-output analysis specifies what needs to be
  done without dictating precisely how it should be
  done, thereby giving workers the responsibility
  of finishing the design based on their knowledge
  of the current context.

8
The traditional information-processing approach

• The best known form of task analysis is that
  based on a human information-processing approach
• It tries to break down molar tasks into their
  constituent elemental information-processing
  steps
• These elemental steps are ordered in a linear
  sequence that progresses from perception to
  decision making to action.

9
A linear sequence of information processing tasks
Activation
Observation
Identification
Interpretation
Task Definition
Procedure Formulation
Evaluation
Execution

1. A signal from the work domain that causes a need
   for a activation or detection.
2. Observation of the work domain
3. Based on the data collected, an identification of
   the current state can be made
4. This state identification can be interpreted to
   determine the consequences for the criteria of
   interest
5. An evaluation can be made to determine which
   criteria are more important and should therefore
   take precedence, for the present situation
6. The task to be pursued can be defined.
7. A procedure for accomplishing the task can be
   formulated.
8. Action is executed.

10
Normans seven-stage model of user activities
11
What descriptive studies show Expert performance

• Task Analysis?? information-processing approach?
  ??
• Not to follow all of the steps in the linear
  sequence
• Not to follow the order that is usually shown.
• Rasmussen (1974) Verbal protocol analysis
• Expert workers take efficient shortcuts
• ?) ??? ????, ?? ??? observation? ??? ??? ???? ??
  procedures ?? ??? ? ? ??.
• To move right to left
• ?) task definition? ??? ??, ??? ??? ????? ???
  ???? ?? ??? ??? ???.
• Novice? Expert? ??
• Expert?? shortcut ? shunt ? ????
• Klein (1989) ??? ?? ???? ??? ????? ??

12
An alternative approach Expertise as an active,
constructive process

• Rasmussen (1976)
• Expertise is the ability to compose a process
  needed for a specific tasks as a sequence of
  familiar subroutines that are useful in different
  contexts.
• 1. Develop a set of subroutines
• ?? ???? ?? ? ? ??? subroutines
• 2. Constructive process
• Generate a contextually tailored sequence of
  cognitive activities that is appropriate for the
  present situation.
• ?, ?? ??? ??? ???? ?? ???.
• 3. Combine 1? 2??
• Retain the flexibility to string together those
  routines in different ways

13
Implications for control task analysis

• Expert performance? ??? ?? control task analysis?
  ??? ??? ????
• ? ?? ??? ???? (CTA) expert action ? ???? ????
  computer-based information systems? ?? ? ? ??.
  (cognitive efficiency? ?? ?)
• ?? ??? ???? ?? expert? ???? subroutine?? ???
  ????, ??? ???? ?? subroutine?? ?? ? ? ??
  flexibility? ????. (Tool Decision ladder)

14
The Decision ladder

• Rasmussen (1974, 1976) ??
• HIP steps?? ??
• By bending a linear sequence of
  information-processing steps in half and adding
  shortcuts that connect the two sides of the
  ladder.

15
Decision Ladder
16
Basic Structure (1)

• State of knowledge versus information-processing
  activities
• ? Data processing activates (??)
• ? State of knowledge (????)
• Information process activities ?? expert routines
  ? ??
• ????? ?? ??? ????? ???
• One box??? ?? box? ?? ?? ?? ???
• Opportunistic movement
• Two sides? ???? shortcut? expert? ?? ?? ????
  stereotypical process?.
• Shunt ? ?? ??
• Leaps ? ? circle ??? link
• Ex) ??? ??? ?? ??? ????? ??? ??? ????? ?? ??? ???
  ? ??.
• ??? starting points

17
Leaps and Shunting
Causal Reasoning
Causal Reasoning
Associative leaps
Shunting paths
18
Basic Structure (2)

• Template, not a model
• The DL is not a model of the decision process
  itself, but rather a map useful to represent the
  structure of such a model.
• DL is a skeleton without any flesh
• To use DL as a scratchpad to identify the control
  task requirements for a particular work domain.
• What, not how or who
• The DL can be used to help determine what
  information-processing activities needs to be
  done, independently of who is to do them and how
  they can be done
• To be used to develop a product description
  rather than a process description
• Formative (???)
• The overall objective is to determine how
  computer-based support systems could be designed
  to allow workers to effectively meet the
  challenges they face.
• It is important that the analyst identify all
  feasible shortcuts
• To foster expert performance. (Shortcuts)

19
Basic Structure (3)

• Grain of analysis
• ??? ?? ????? ? ? ?? ??(??)??? ? ? ??.
• Hospital ?? control task analysis ? ?
• Fine level of analysis Low-level activity
• (ex) ???? ???? drag??
• Activation information-processing activity
  require detecting that a patient is in pain and
  needs analgestic.
• Coarse level of analysis High-level activity
• (ex) Human resource management
• Activation information-processing activity
  require detecting a need to hire more qualified
  personnel
• ? ????? ???? ??? ??? ??? ? ??.
• Operating modes
• In process control plants plant setup, normal
  operation, disturbance management and plant
  shutdown
• In hospitals preoperative, surgery recovery
• The DL can be used as a template in each case,
  but each mode will use a different template to
  identify the information requirements associated
  with that mode

20
Decision ladder of ADS? ??

• ???? action? ?? constrains? control task ?? ???
  ?? ??
• Work domain ??? ?? constraints (CWA? 1??)
• Information-processing activities?
• ??? work domain ??? ?? ??? ??????
• Work domain? functional structure? ??????
• ??? ?? control task? ??? constraints? ??????
• ????? ??? ? ? ?? work domain???? ??? ?????? ????.
  
• ????? worker?? ?? work domain ??? ??
• ?? actor? ?? actor ??? ???? ????(supervisory)
• Supervisory work domain??? ???? automation? ??

21
A simplified diagram of the relation between ADS
and DL
22
Multiple uses of the Decision ladder

• DL? ?? ?? ???? ??
• As a template in identifying the requirements
  associated with particular information-processing
  activities
• ??? ?? ????(requirement)?? ?? ????? ????? ???? ??
• Verbal pastoral analysis ???
• Two examples from Rasmussen (1980)
• Scheduled order? ?? ??? ???? ??
• Alarm signal? ?? ????

23
How verbal protocols can be mapped on the DL
Evaluate
Evaluate
Evaluate
Performance Criteria
Performance Criteria
Performance Criteria
Ambiguity
Ultimate Goal
Ambiguity
Ultimate Goal
Ambiguity
Ultimate Goal
Interpret
Interpret
Interpret
Yes !
System state
Goal State
System state
Goal State
System state
System state
Goal State
Goal State
Define Task
Define Task
Define Task
Identify
Identify
Identify
Then
(Schedule, order) We now have to
Set of observation
Task
Task
Task
Task
Formulate Procedure
Observe
System ready ?
Procedure
Alert
Execute
24
Example 1 lt??gt

• Receiving a scheduled order
• Not have to engage in any information-processing
  activities
• He knows that task to perform
• Alert See if the work domain is ready to
  process the order
• Based on experience, a leap between two states of
  knowledge
• Between knowledge of the order and knowledge to
  check work domain readiness
• Observe the work domain
• Knowing system state
• Based on experience, a shunting path
• The worker determine the state of the work domain
  by collecting data and without having to engage
  in the additional information processing activity
  of identification
• Knowing procedures
• Leap from system state ? procedure
• Execute the appropriate actions in the procedure

25
(No Transcript)
26
Example 2 lt??gt

• Activation The worker detects the need for
  action
• Alert The output of activation (whats that?)
• Observe
• To answer this question (whats that?)
• The worker collects information about the state
  of the work domain
• System state Shunt (observation ? system state)
• Be able to directly determine the cause of the
  alarm, without having to integrate the observed
  data by engaging in identification.
• Task Leap (system state ? task)
• The worker knows what task needs to be performed
  to clear the alarm
• Procedure Leap (task ? procedure)
• The worker is familiar with task, not have to
  formulate a procedure
• Execute the appropriate actions in the procedure

27
Control task analysis for process control
microworld

• Operating Modes
• Start-up shutdown ????? start-up, 4? ?? ??
• Normal operation moving from one set of demand
  set point to another
• System shutdown Bringing the work domain to a
  zero state
• Fault management coping with equipment failure
  and other disturbances
• To conduct a separate control task analysis for
  each operating mode
• Only the star-up mode analysis

28
DL for Start-up in DURESS II
29

• 1. Goal state
• The required temperature? output demand value? ?
  ??? ?????
• T1 set point tolerance, MO1 set point
  tolerance
• Set point value? ???? ???, actor? goal state? ??
  ??? ?? ??.
• 2. Goal state iteration
• ?? ??? ????? ??? ? ?? sub goal ? sub- sub goal?
  decomposition.
• ????? mass inventory ? energy inventory?(first
  level)
• Demand ??? mass inventory? (first level)
• Energy inventory? ???? ?? ?? input energy ? ???
  ?? (second level)
• Mass inventory? ???? ?? ?? input mess? ??? ??
  (second level)
• Recursive leaps ? expert? ????? ? ? ??

30

• 3. Define task
• ? ????? ?? ????
• Energy input goal ? ??? ?? ???? heat transfer
  rate? ??
• Mass input goal? ??? ?? ??? water input flow
  rate? ??
• ??? ??? (heat transfer and flow rate values)
  generalized function level of abstraction?? ???.
• Actor?? ??? ?? constraint? ??? ?.
• Conservation of mass in reservoir
• Conservation of energy in reservoir
• ? ???? heat transfer (FHI)? water input flow
  (MII)? ?? ?? ?? ??(TI and Mol)? ??? ??? ????? ??.
• 4. Task
• The outputs of the two define task activities
• Actor ?? ???? FH1 (heat transfer rate)? ???? MI1
  (water input flow rate)? ?? ??.

31

• 5. Formulate procedure
• To derive plan of actions
• Appropriate heater setting ? desired heat
  transfer rate ??
• Appropriate set of valve and pump settings ?
  desired water input flow rate ??
• Actor ?? ???? ?? ?
• Heater configuration (??) heater setting(HTR1)
  value ? Desired heat transfer (FH1) value
• FWS configuration (??) component setting (PA VA
  VA1 VA2)? ? desired water input flow(MI1) ?
• ?? ??
• ? ?? heater ?? ??
• Valve? ?? ?? pump?? ??
• 6. Procedures
• Actor?? ???? component setting ????.
• ? setting? ??? ??? ???? constraints? ???? ?? ???
  ????.

32

• 7. Execute
• Component? ??? actor? ??, components setting ?
  ???
• 8. Alert
• State of vigilance (Work domain? ??? monitor? ??)
• 9. Observe
• To observe the approach of the goal variables to
  their respective desired values to determine the
  appropriate time to act to stabilize the work
  domain state
• ????? ??
• TI(????)? set point value? ??? ??? ?
• Time to contact ??? ??? ??? ??? ???? higher
  order variable
• Output demand goal? ??
• Output value? ??? open ?? ??? volume? ??? no
  inflow??, output flow rate? zero? ? ??? ??? ?? ?
  ? ??.
• ???? overflow???, empty???, steady?? ???? ? ??
  ??? ??.
• Actor? ??? ??? ?? ?? single ideal value? ??.
• Volume setting? ???? temperature ??

33

• 10. Task
• Shunt observe box ? task circle.
• 11. Formulate procedure
• Output demand goal? ??
• Output value (VO1)? ? setting ???? ?? (Output
  flow rate (MO1)? goal region? ???)
• Temperature goal? ??
• The heater (HTR1) is set so that the temperature
  (T1) rests in the region
• 13. Procedure
• A sequence of specific actions comprising the
  valve and heater settings that will achieve the
  aforementioned task
• 14. Execute
• Timing is very important in this step
• Start up mode ??

34
Discussion (1)Highlighting the key points

• Constraint based
• Idealized flow sequence? ??? control? ??
  constraint?? ????.
• ?? actor?? ??? ??? ? ??.
• ?? ???? heater? maximum? ?? ? aggressive manner
• ?? ???? hearer? low??? ?? ? conservative manner
• It provides a great deal of guidance by
  specifying what constraints must be dealt with to
  achieve the control tasks reliably and
  effectively
• Each information-processing activity represents a
  function that transforms a given set of inputs
  into a given set of outputs according to a
  specific set of constrains
• CTA provides an envelope within which actors can
  operate
• This envelope supports the goal-directed,
  adaptive flexibility that is the hallmark of
  context-conditioned variability

35
Discussion (2)Highlighting the key points

• 2. opportunistic
• ???? ???,
• Several of the information-processing activities
  and state of knowledge were not used
• 3. Just a template but still very useful
• DL is just a template.
• All of the content had to be obtained from
  sources other than the ladder
• 4. What, Not How or Who
• Referring to a hypothetical actor rather than a
  worker or automation
• To identify the requirements that must be
  satisfied by actors
• 5. Formative
• Information requirement identification not
  descriptive fashion

36
Discussion (3)Highlighting the key points

• 6. Action mean-ends (CTA)
• Structured mean-ends Work domain analysis
• Describing what needs to be done with those
  objects and functions
• ?) FWS (structured means) ? Act of configuring
  the FWS (action means)
• ?) heater (structured means) ? Act of changing
  the heater setting (action means)
• 7. Relationship to work domain analysis
• CTA inherits the layer of constraints identified
  in a work domain analysis, while simultaneously
  adding a new nested layer of constraint

37
Summary and implication

• CTA the second phase of CWA
• Because of DLs shortcuts,
• It provides a template that can be used to
  determine only those activities that are required
  to exhibit expert action, thereby fostering and
  supporting efficient and flexible performance
• This representation
• Can be used to design procedures, automation, and
  context-sensitive interfaces
• Ex) the relationship between FWS valve settings
  and the resulting flow into the reservoir could
  be used to design a computer-based aid that would
  suggest a viable set of component settings.
• Ex) a task specific display to present the time
  to contact the temperature directly.

38
Summary
Cognitive Work Analysis Framework
Cognitive Work Analysis
Systems Design
Identify
Form
Realize
Build
Develop
Conceptual Distinctions
Modeling Tools
Models of Intrinsic Work Constraints
Systems Design Interventions
v
1. Work Domain
1.
1.
1. Sensors, models, database
Abstraction- Decomposition
v
2. Control Tasks
2.
2.
2. Procedures, automation, context-sensitive
interface
Decision ladder
3. Strategies
3.
3.
3. Dialogue modes, process flow
4. Social-Organizational
4.
4.
4. Role allocation, organizational, structure
5. Worker Competencies
5.
5.
5. Selection, training, interface form