1 Chapter 8 : Phase II : Control Task Analysis 홍 승 권홍 승 권홍 승 권홍 승 권.

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Chapter 8 : Phase II : Chapter 8 : Phase II : Control Task AnalysisControl Task AnalysisChapter 8 : Phase II : Chapter 8 : Phase II : Control Task AnalysisControl Task Analysis

홍 승 권 홍 승 권

Contents1. Purpose2. 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 proc

ess Implications for control task analysis

3. Decision ladder Basic structure Relationship between the decision ladder and the abstraction-dec

omposition space Multiple uses of the decision ladder: Some examples

4. Control task analysis for process control microworld Operating modes Set-up Discussion: Highlighting the key points

5. Summary and implications

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Purpose

CWA (Cognitive Work Analysis) 의 두 번째 단계To 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 whomDURESS II Process control case studyModeling tool = decision ladderCTA 와 WDA 사이의 상호관계

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Different approaches to analyzing control tasks

Chapter 3 (three types of task analysis approaches)– Input-output (Constraint-based analysis) : For complex soc

iotechnical systems– Sequential flow (Instruction-based analysis)– Timeline (Instruction-based analysis)

Additional considerations (TA 방법 선택을 위해 )– To identify the requirements that are associated with expe

rt action– Expert 를 지원하는 information systems

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What is control task analysis?

(Control task analysis 의 세가지 특성 )

1. CTA 의 목적이 무엇이며 , WDA 의 목적과 어떻게 다른가 ?– CT 와 WD 의 관계 (Input-output of CT)

• Control task 는 Work domain 상태에 대한 정보를 필요로 함 (INPUT side).

• Control task 는 Work Domain 상에서 행동 (OUTPUT side)

– Work Domain Analysis 는 task, event goal 과 독립적이지만 , 일단 WDA 가 수행된 후에는 수행할 Goal 을 생각

• 상황에 따라 달라지는 Goal (beach 에서 개미의 목적 )• Goal 이 결정되면 고려되는 Work Domain 의 부분도 다름 ( 먹이를 찾을

때와 짐에 갈 때 )• 각 class 와 관련된 requirement 를 식별해야 함 .

– 일반적으로 , 특정 도메인에서 알려진 event class 에 관련된 requirement 을 식별하는 것이 Control task analysis.

– Noun 에 대한 강조가 verb 에 대한 강조로 (WD → CT)

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Control task 와 Work domain의 관계

Control Tasks

Work Domain

Act-onInformation-to

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2. CTA describes only what needs to be done, not how or whom

– How tasks can be done ( 어떤 전략 전에 )– How should be allocated to different actors ( 누가 수행

전에 )– 즉 , 전략이 수행하는 목표 , allocate 해야 할 것에 대한 것

3. Open System (complex socio-technical systems)– They require context-conditioned variability to adapt

to disturbances– 같은 목표가 다른 상황에서 다른 방법들에 의해 수행되어야 함– 이러한 Requisite variability 를 만족시키기 위해 Input-

output 분석이 요구됨 .– 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.

What is control task analysis? (Control task analysis 의 세가지 특성 )

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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.

A linear sequence of information processing tasks

Activation

Observation

Identification

Interpretation

Evaluation

Task Definition

Procedure Formulation Executio

n

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.

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Norman’s seven-stage model of user activities

GOALS

Evaluation

Interpretation

Perception

Intention

Action specification

Execution

Physical Activity

Mental Activity

“Expectation”

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What descriptive studies show: Expert performance

Task Analysis 에서 information-processing approach 의 단점– 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

• 예 ) 친숙한 상황에서 , 단지 간단한 observation 을 통하여 그들이 수행해야 하는 procedures 들을 명확히 알 수 있음 .

– To move right to left• 예 ) task definition 이 완료된 후에 , 요구된 작업을 수행하기에 적절한

상태인지 보기 위하여 공장을 관측함 .

Novice 와 Expert 의 차이– Expert 에게 shortcut 과 shunt 는 일상적임– Klein (1989) 연구와 유사 : 전문가는 경험과 사전지식에 의존

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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– 다른 상황에서 사용 될 수 있도록 subroutines

2. Constructive process– Generate a contextually tailored sequence of

cognitive activities that is appropriate for the present situation.

– 즉 , 미래 계획된 해답을 인출하는 것이 아니다 .3. Combine 1 과 2 혼합

– Retain the flexibility to string together those routines in different ways

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Implications for control task analysis

Expert performance 에 도움이 되는 control task analysis 를 어떻게 실시할 것인가 ?

본 접근 방법을 수행하면 (CTA) expert action 을 유도하고 지원하는 computer-based information systems 을 설계 할 수 있다 . (cognitive efficiency 을 얻는 것 )

이런 목적을 달성하기 위해 expert 가 사용하는 subroutine 으로 작업을 분할하고 , 다양한 방법으로 이런 subroutine 들은 조합 할 수 있는 flexibility 을 제공하자 . (Tool: Decision ladder)

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The Decision ladder

Rasmussen (1974, 1976) 개발HIP steps 과의 관계

– By bending a linear sequence of information-processing steps in half and adding shortcuts that connect the two sides of the ladder.

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Decision Ladder

Data processing activities

State of knowledge resulting from data processing

Evaluate Performance Criteria

Define Task

Interpret

Identify

Alert

Execute

System state

Ambiguity Ultimate Goal

Goal State

Task


Define Task

Interpret

Identify

Activation

Formulate Procedure

Execute

System state


Goal State

Task


Define Task

Interpret

Identify

Observe

Execute

System stateSystem state

Set of observation


Goal StateGoal State

TaskTask

Procedure

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Basic Structure (1)

State of knowledge versus information-processing activities– □ : Data processing activates ( 활동 )– ○ : State of knowledge ( 지식상태 )– Information process activities 들은 expert routines 에 해당– 인지활동을 통해 새로운 지식상태가 구현됨

• One box 로부터 다른 box 로 직접 가는 것은 불가능 Opportunistic movement

– Two sides 을 연결하는 shortcut 은 expert 에 의해 종종 채택되는 stereotypical process 다 .

– Shunt : □ →○ 연결– Leaps : 두 개 circle 사이의 link

• Ex) 시스템 상태에 대한 지식이 직접적으로 수행할 작업이 무엇인지에 대한 지식과 연계될 수 있음 .

– 다양한 starting points

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Define Task

Interpret

Identify

Alert

Execute

System state


Goal State

Task


Define Task

Interpret

Identify

Activation

Formulate Procedure

Execute

System state


Goal State

Task


Define Task

Interpret

Identify

Observe

Execute


Set of observation



TaskTask

Procedure

Causal Reasonin

g

Causal Reasonin

g

Shunting paths

Associative leaps

Leaps and Shunting

Basic Structure (3) Grain of analysis

– 경우에 따라 세밀분석이 될 수 있고 대충 ( 개략 ) 분석이 될 수 있음 .– Hospital 에서 control task analysis 의 예1. Fine level of analysis : Low-level activity

• (ex) 환자에게 투여되는 drag 관리• Activation information-processing activity require detecting that a patient is in pain and n

eeds analgestic.2. Coarse level of analysis : High-level activity

• (ex) Human resource management• Activation information-processing activity require detecting a need to hire more qualified

personnel → 분석목적이 결정되면 분석의 수준도 결정될 수 있다 .

Operating modes– In process control plants : plant setup, normal operation, disturbance managemen

t 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 differen

t template to identify the information requirements associated with that mode

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Decision ladder of ADS 의 관계 일어나는 action 에 대한 constrains 는 control task 구조

때문인 것도 있고 – Work domain 구조에 의한 constraints (CWA 의 1 단계 )

Information-processing activities 는 – 현재의 work domain 상태에 대한 정보를 인지함으로써 – Work domain 의 functional structure 를 인지함으로써– 대상이 되는 control task 와 관련된 constraints 을 인지함으로써– 상태변화에 영향을 줄 수 있는 work domain 상에서의 행동을

인지함으로써 수행된다 . 전형적으로 worker 들은 같은 work domain 상에서 행동

– 어떤 actor 는 다른 actor 위에서 행동하는 계층구조(supervisory)

– Supervisory: work domain 상에서 행동하는 automation 을 감시

A simplified diagram of the relation between ADS and DL

Decomposition

Abstraction

Decision Ladder

Act-onInformation-to

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Multiple uses of the Decision ladder

DL 은 여러 가지 목적으로 사용– As a template in identifying the requirements

associated with particular information-processing activities

– 어떻게 이런 정보요구 (requirement) 들이 여러 사람들에게 분배할까를 결정하기 위해

– Verbal pastoral analysis 도구로Two examples from Rasmussen (1980)

– Scheduled order 를 받고 작업을 시작하는 경우– Alarm signal 을 받고 작업시작

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Define Task

Interpret

Identify

Alert

System state


Goal State

Task


Define Task

Interpret

Identify

Formulate Procedure

System state


Goal State

Task


Define Task

Interpret

Identify

Observe

Activation Execute


Set of observation



TaskTask

Procedure

How verbal protocols can be mapped on

the DL

Then …

System

ready ?

Yes !

(Schedule, order) We now have to …

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Example #1 < 설명 >

1. Receiving a scheduled order– Not have to engage in any information-processing activities– He knows that task to perform

2. 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 readiness3. Observe the work domain4. 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

5. Knowing procedures– Leap: from system state → procedure

6. Execute the appropriate actions in the procedure

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Define Task

Interpret

Identify

Alert

System state


Goal State

Task


Define Task

Interpret

Identify

Formulate Procedure

System state


Goal State

Task


Define Task

Interpret

Identify

Observe

Execute


Set of observation



TaskTask

Procedure

We then have to…

What’s

that ?

Activation

Signal,

alarm

Oh, that is ...

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Example #2 < 설명 >

1. Activation : The worker detects the need for action2. Alert : The output of activation (what’s that?)3. Observe

– To answer this question (what’s that?)– The worker collects information about the state of the work

domain

4. 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.

5. Task : Leap (system state → task)– The worker knows what task needs to be performed to clear the

alarm

6. Procedure : Leap (task → procedure) – The worker is familiar with task, not have to formulate a

procedure

7. Execute the appropriate actions in the procedure

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Control task analysis for process control microworld

Operating Modes– Start-up : shutdown 상태로부터 start-up, 4 개 목표

수행– 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 disturbancesTo conduct a separate control task analysis

for each operating modeOnly the star-up mode analysis

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Define Task

Interpret

Identify

Alert

System state


Goal State

Task


Define Task

Interpret

Identify

Formulate Procedure

System state


Goal State

Task


Define Task

Interpret

Identify

Observe

Execute


Set of observation



TaskTask

Procedure

Activation⑬

②①

③

⑤

④

⑥

⑦

⑧

⑨

⑩

⑪

⑫

DL for Start-up in DURESS II

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1. Goal state– The required temperature 와 output demand value 로 각

수조를 안전화시킴– T1= set point ± tolerance, MO1= set point ± tolerance – Set point value 가 주어졌기 때문에 , actor 는 goal state 에 대한

지식을 갖고 시작 .2. Goal state iteration

– 전체 목표가 직접적으로 달성될 수 없고 sub goal 과 sub- sub goal 로 decomposition.

– 온도목표는 mass inventory 와 energy inventory 로 (first level)– Demand 목표는 mass inventory 로 (first level)– Energy inventory 를 조정하기 위해 먼저 input energy 의 흐름을

조정 (second level)– Mass inventory 를 조정하기 위해 먼저 input mess 의 흐름을 조정

(second level)– Recursive leaps → expert 는 자동적으로 할 수 있음

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3. Define task – 각 목표달성을 위한 과제정의– Energy input goal 을 맞추기 위해 바람직한 heat transfer rate

를 선택– Mass input goal 을 맞추기 위해 적절한 water input flow rate 를

선택– 적절한 정보는 (heat transfer and flow rate values)

generalized function level of abstraction 에서 발견됨 .– Actor 들은 다음과 같은 constraint 를 알아야 함 .

• Conservation of mass in reservoir• Conservation of energy in reservoir

– 이 수식들은 heat transfer (FHI) 과 water input flow (MII) 의 값이 상위 목표 상태 (TI and Mol) 에 어떻게 영향을 미치는지를 보임 .

4. Task– The outputs of the two “define task activities”– Actor 들은 바람직한 FH1 (heat transfer rate) 과 바람직한 MI1

(water input flow rate) 을 알고 있음 .

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5. Formulate procedure– To derive plan of actions– Appropriate heater setting → desired heat transfer rate 달성– Appropriate set of valve and pump settings → desired water

input flow rate 달성– Actor 들이 고려해야 하는 것

• Heater configuration ( 수식 ) : heater setting(HTR1) value → Desired heat transfer (FH1) value

• FWS configuration ( 수식 ) : component setting (PA VA VA1 VA2) 값 → desired water input flow(MI1) 값

– 다른 절차• 물 없이 heater 켜지 마라• Valve 를 열지 않고 pump 하지 마라

6. Procedures– Actor 들은 바람직한 component setting 이해한다 .– 이 setting 은 위에서 설명된 연속적인 constraints 를 위배하지 않는 순서로

수행된다 .

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7. Execute– Component 의 위치를 actor 를 알고 , components setting 을 바꾼다

8. Alert– State of vigilance (Work domain 의 상태를 monitor 할 준비 )

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

– 온도목표를 위해• TI( 현재온도 ) 와 set point value 를 모니터 되어야 함• Time to contact : 현재와 목표치 사이의 차이의 변화율은 higher order variable

– Output demand goal 을 위해• Output value 가 적절히 open 되어 있지만 volume 이 없거나 no inflow 이면 ,

output flow rate 는 zero 가 될 것이고 목표는 달성 될 수 없다 .• 저장소에 overflow 가능성 , empty 가능성 , steady 상태 도달시간 등 많은 변수가 있다 .• Actor 가 행동할 시간에 대한 정보 : single ideal value 는 없다 .

– Volume setting 이 선행되고 temperature 맞춤

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10. Task– Shunt : observe box → task circle.

11. Formulate procedure– Output demand goal 을 위해

• Output value (VO1) 이 잘 setting 되었는가 확인 (Output flow rate (MO1) 이 goal region 에 있도록 )

– Temperature goal 을 위해• 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 완성

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Discussion: (1)Highlighting the key points

1. Constraint based– Idealized flow sequence 가 아니라 control 에 대한 constraint 만을

얘기한다 .– 다른 actor 들은 다르게 행동할 수 있음 .

• 어떤 사람들은 heater 를 maximum 에 놓고 → aggressive manner• 어떤 사람들은 hearer 를 low 상태에 놓기 → 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

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2. opportunistic– 시작점도 다르고 , – 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 ladder4. 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

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6. Action mean-ends (CTA)– Structured mean-ends : Work domain analysis– Describing what needs to be done with those objects and

functions– 예 ) FWS (structured means) → Act of configuring the FWS

(action means)– 예 ) 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

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Summary and implication CTA : the second phase of CWA Because of DL’s 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.

Build

Summary

Conceptual Distinctions

Modeling Tools

Models of Intrinsic Work Constraints

Systems Design

Interventions

FormDevelopRealizeIdentify

CognitiveWork Analysis

Framework

CognitiveWork

Analysis

SystemsDesign

1. Work Domain

2. Control Tasks

3. Strategies

4. Social-Organizational

5. Worker Competencies

1.

2.

3.

4.

5.

1.

2.

3.

4.

5.

1. Sensors, models, database

2. Procedures, automation,

context-sensitive interface

3. Dialogue modes, process

flow

4. Role allocation,

organizational, structure

5. Selection, training,

interface form

vAbstraction-Decomposition

Decision ladder v

1 Chapter 8 : Phase II : Control Task Analysis 홍 승 권홍 승 권홍 승 권홍 승 권.

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