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Chapter 7 : Phase I : Chapter 7 : Phase I : Work Domain AnalysisWork Domain AnalysisChapter 7 : Phase I : Chapter 7 : Phase I :

Work Domain AnalysisWork Domain Analysis

홍 승 권 홍 승 권

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Contents

1. Purpose2. The importance of field descriptions3. The abstraction-decomposition space4. More about the abstraction hierarchy5. Work domain analysis for process

control micro-world6. Summary and implications The

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Purpose To explain work domain analysis which is the

first phases of CWA– To explain the nature of field descriptions– To describe Rasmussen’s(1979, 1985) abstraction-

decomposition space : WDA tool– To explain the detailed AH – To show an examples of how the abstraction-

decomposition space can be used to conduct a work domain analysis

To understand why work domain analysis identifies a fundamental set of constraints on the actions of any actor

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The importance of field descriptions

Field Description = Work Domain Representation

시스템 안전을 위협하는 것들은 Designer 나 Worker들에게 친숙하지 않았던 것

3 장에서 보았듯이 Task Analysis 가 이런 것을 충족시켜주지 못하므로 , 새로운 것에 대처하기 위해서는 event-Independent representation 필요– Map ← Direction– Work domain representation ← Task representation

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Simon’s parable about an ant(1981)

기하학적 도형의 관점에서 보았을 때 개미의 이동경로는 복잡

개미의 심리적 constraints + 해변의 constraints 행위자체 보다는 환경에 대한 이해가 중요The environment is relevantly invariant over

particular initial conditions, task goals and trajectories

해변의 구조가 어떤 상황에서도 개미의 행동에 대한 constraints 가 되는 것처럼 , WD 의 기능구조(functional structure) 는 actor 의 action 에 constraints 이다 .

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Kinematics vs Dynamics (Trajectories vs Fields)

A magnetic filed is created by two fixed positively charges particles

When a negatively charged object is place, How would the field change?

Kinematics : the study of motion (trajectories)– Objects are described in terms of state variables such as

position, velocity, acceleration and so on– To describe motions

Dynamics : the study of the forces that shape motion– Objects are described in terms of structural parameters such

as damping constants and spring constants– To predict possibilities for motion

Field Strength

Position

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Gibson and Crooks’ (1938) field description

The field description can also be applied to psychological problem – The other example : Kirlik, Miller & Jagacinski (1993)

Their key insight was that the constraints on behavior can be identified by developing a functional description of the work domain

To use an action-relevant language to describe those objects, such as obstacle, collision, path and destination rather than adapting a context-free language to describe objects in the work domain

The result : Field of safe travel – Field description represents the possible paths that the car may

safely follow– Field of safe travel is a description of work domain, not of the ta

sk– The field describes constraints on action, not action itself

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Field of safe travel

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Comparison of various analogues used to show the difference between work domain and task analysis

Navigation Map Directions

Simon’s Parable Beach Ant’s actions

Mathematics & Physics

Field Dynamics Predict possibilitiesPossibilities for motionStructure

Trajectory KinematicsDescribe instances Motion Behavior

Automobile Driving

Field of safe travel Driver’s actions

Work Analysis Work domain Tasks

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The abstraction-decomposition space (ADS)

Rasmussen (1979, 1985)– A two-dimensional modeling toll that can

be used to conduct a work domain analysis

이 section 에서 할 일 – 어떻게 abstraction-decomposition space 가

Field description 으로 사용될 수 있는가 ?– 다른 종류의 hierarchy 와 abstraction and

decomposition hierarchy 가 다른 점은 ?

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An example of ADS

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An example of ADSA professional electronic technician engaged

in troubleshooting computer equipmentEach node – one verbal statement (by verbal

report)The sequence of nodes (1 to 15) represents

a trajectory of the verbalized cognitive activities of one technician

ADS– Decomposition represents a different level of

granularity– AH spans the gap between purpose and material

form

An Example of ADS

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An example of ADS세가지 ADS 는 다른 Trajectory 를 표시

– The same task (electronic troubleshooting)– To show a great deal of variability in the

trajectories that were taken across particular cases Knowing the structure of the field gives us

some insight into why trajectories may differ across instances.

Knowledge about the functional structure of the work domain, represented in the form of an abstraction-decomposition space, shows the degree of freedom that actors have available for action

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다른 계층구조와의 차이점

Car

Tire Battery

Mammal

Dog Cat

Baseball

Manager

First-Base Coach

Third-Base Coach

Warmth

Fireplace Furnace

다른 계층구조와의 차이점계층구조의 차이점

– The nature of the relationship between levels

– Example of different relations : spatial scale, temporal scale, authority, flow of information, etc.

First type- Authority hierarchy– To have authority over all

of the below nodes– To be subordinate to all of

the above nodes

Baseball

Manager

First-Base Coach

Third-Base Coach

다른 계층구조와의 차이점Second type

– To be based on a classification or “is-a” link

– To be super-ordinate category for all of the below nodes

– To be a exemplar of all of the above nodes

Third type : Decomposition– To be defined by a part-whole

link– To be made up all of the below

nodes– To be a part of all of the above

nodes

Mammal

Dog Cat

Car

Tire Battery

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다른 계층구조와의 차이점The fourth type

– a structural means-ends link

– To be the end that can be achieved by all of the below nodes

– To be a structural means that can be used to achieve all of the above nodes

Warmth

Fireplace Furnace

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Different Mean–Ends LinkNewell & Simon (1972)

– Action mean – ends link (More popular)– Going down to the basement and then lighting the

fireplace are both means for achieving warmth– Two means are actions, not objects (verb phrases)

Furnace and fireplace (Structural Mean-end relationship)– Object that can be used to achieve warmth (Noun)

Work domains are object of action, while a task analysis represents the goals to be achieved by actor’s action (Table 7.1 참조 )

To describe the thing being controlled, we need a relation that represents the structure of the object of action, not the structure of actions themselves.

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More about the AH

1. To describe the generic properties of the AH2. To review some evidence that the AH is a

psychologically relevant way of describing complex STS.

3. To review the arguments that the AH can be used to identify the information support that workers need to cope with disturbances that have no been anticipated by designers

4. To describe some hints for conducting work domain analysis

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Stratified HierarchiesThe AH belongs to the class of stratified hierarchie

s described by Mesarovic et al. (1970), The properties of which are listed here

– 다른 계층은 같은 시스템에 대한 다른 서술– 각 층은 고유한 set of terms, concepts, and principles

갖음 . – 특정 시스템을 서술하기 위해 계층의 선정 ( 수 , 선정

레벨 ) 은 관측자 , 그들의 지식 그리고 시스템 통제에 대한 그들의 관심에 달려있음 .

– 특정 레벨에서의 요구사항은 낮은 레벨에 대한 constraints 로써 나타내고 , 시스템 상태의 변화는 높은 레벨에 대한 낮은 레벨의 영향에 의해 기술됨

– 시스템에 대한 이해를 높이기 위해 레벨을 상하로 이동

Five levels of constraints

Functional Purpose

Domain properties represented

Purposes and constraints

The purposes for which the system is being designed

Abstract functions and priority measures

The intended causal structure of the work environment represented in terms of the flow of values and abstract physical properties

General functions Description of the basic process of the system in functional language

Physical processes and activities

Characteristics of the physical components associated with these processes and their connections

Physical form and configuration

Characteristics of appearances and special distribution of physical components

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Psychological Relevance

중요한 특성의 하나– AH 가 Complex work domain 를 표현하는 psychological

유용한 방법 There are many different ways to represent a work

domain– Algebraic and state equations (DURESS II 에서 )– 직관적으로 인식할 수 있는 표현이 중요

From a psychological perspective, – One of the most important features of an AH is that

higher levels are less detailed than lower levels (AH 만의 특성은 아님 )

• This provides a mechanism for coping with complexity

– AH is explicitly purpose-oriented• A structural means-end relation provides a very important

source of constraint that can be exploited by actors : 현재의 관심기능과 관련 있는 function level 만 찾음

Three goal-oriented questions: Why? What? How?

Subjective Mental

Workload

NASA TLX

SWAT

Performance

Reaction Time

Error

Paper Form

Paper Form

Stopwatch

Video Camer

a

Computer

Why ?

How ?

What ?Why

?

How ?

What ? Why

?

How ?

What ?

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Three goal-oriented questions: Why? What? How?

The linkages between the three questions and the levels of the hierarchy are not absolute in any sense.

AH identifies the structural WD constraints on achieving goals

There can be many-to-many mappings between nodes at various levels of abstraction– Reaction time ↔ computer and stopwatch– This provides people with a way to cope with that

complexity

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Coping With the Unanticipated

중요한 특성의 하나– AH 는 작업자가 예상치 못한 사건을 다루는데 필요한 정보를

식별하고자 할 때 base 를 제공 A disturbance results in the breaking of one or more

constraints that govern the work domain under normal circumstances (Rules of rightness)– The task of disturbance detection is equivalent to

detecting the breaking of constraints The complete set of goal-relevant constraints

governing the work domain must be represented to permit workers to determine when a constraint has been broken, and thereby allow them to diagnosis the disturbance

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An example The logic of analytical redundancy

An technique of using multiple constraints to detect and diagnose unanticipated disturbance– In control theory, Analytical redundancy

(Frank, 1990)– Basic idea : 현재 입력 data 를 시스템 모델에 입력 → output

무엇이 되어야 하는지 찾음 → 현재 output 과 기대되는 output 를 비교

– 결과로 나타난 차이는 시스템이 작동해야 하는 것과의 차이를 나타냄 – AH 가 유일한 방법이 아님

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To illustrate how analytical redundancy provides a way of coping

with the anticipated.

구성 :

1. Input Valve (VIN)

2. Output Valve (VOUT)

3. A reservoir holding water (level 0 to 100)

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An example : water flow process

One of constraints that governs the process : the law of conservation of mass– The other constraints could

be identified

What kind of disturbances – A leak of reservoir– 빗물이 들어감– 화재로 인해 저장소 물을 사용– 채워 넣기 등 ( 설계자가 예상 못한

사건들 )

density

rate flowoutput mass)(

rate flowinput mass)(

levelor volumereservoir )(

)()()(

tMO

tMI

tVol

tMOtMI

dt

tdVol

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An example 잘못된 모든 상황을 이해하려고 하지 말자대신에 work domain 이 정상적으로 작동하는

상황을 정의하자– 즉 Work domain constraints 들이 무엇을 하는지 정의– When constraints are violated, there is an

indication that something is wrong 예를 들어 ,

– 어떤 event 는 mass balance constraints 에 영향을 줌 .

– 작업자는 constraint 와 관계된 모든 변수에 대한 정보를 암– 이들 변수들의 정상적인 상호관계도 암– 작업자는 violated constraint 를 인식함으로써

disturbance 를 식별할 수 있음

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Hints for conducting a WDA① Define a boundary

특별한 방법 없음 – interaction 이 약한 부분을 경계로 사용② Use a matrix diagram as an overview of the various

representation③ To begin by constructing the part-whole Hierarchy

Modeling (action) 이 가능한 level 까지만 decompose④ Decomposition 과정에서 , 아래 레벨과 윗 레벨의 상관관계

고려⑤ AH representation 과정에서 , the top level and the

bottom two levels 을 먼저 시작 가능한 많은 level 사용 여러 가지 목적을 갖는 시스템에서 각 Goal 을 위한 AH

representation 을 먼저 제안한 후에 combine 함 . ⑥ action means–end 와 structural means–end 구별하여

생각

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Hints for conducting a WDA⑦ AH 각 level 에 모든 nodes 는 같은 modeling languages,

다른 level 은 다른 modeling languages ⑧ Why, what, how question 을 반복적으로 사용⑨ 다른 type 의 Hierarchy 가 들어 가지 않게 : Structural me

an-end link 와 whole-part link 가 혼합되지 않게 주의⑩ Decomposition hierarchy 를 따라 움직이면 , different object

에 대한 기술 ( 예 차와 베터리 ), AH 를 따라 움직이면 , 같은 object 에 대한 새로은 (functional) 기술 ( 예 , warmth와 furnace)

⑪ Your representation 을 여러 번 수정 및 반복⑫ 작은 example 을 참고 하라

Process control microworld (overview)Whole System(Duress)

Subsystem(Reservoir)

Components

Functional Purpose

Abstract Function

Generalized

Function

Physical Function

Physical Form

Outputs to Environmen

tMass/Energy

Topology

Liquid Flow & Heat Transfer

Liquid Flow & Heat TransferComponent

State

Appearance & Location

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Decomposition Hierarchy

- Component level : pumps, valves, heaters, reservoirs- Subsystem level : transport subsystems, storage subsystems, heating subsystems- System level: Whole system

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Abstraction Hierarchy Functional purpose : Work domain purposes,

system level of the part-whole decomposition.① 각 수조에 물의 온도를 set point 에서 유지 (2 개 목적 )② 각 수조에 충분한 물 유지 (2 개 목적 )

Abstraction function: To be described in terms of flow of mass and energy that balances the conservation of mass and energy for each storage subsystem① System → Subsystem② Each subsystem 은 one mass and one energy

store( 수조 ), one source of mass (input water), two source of energy (input water heater), one sink of mass and energy (output value)

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Mean-end links for DURESS II

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Abstraction HierarchyGeneralized function: flows and storage of

heat and water are described at this level of abstraction① Subsystem level : the rate of water heat transfer

(input stream), rate of heat transfer (heating system), heat storage and water storage (reservoirs), rate of removal of heat and water

② Components level :

Physical function: the states of the component ① Valves, pumps and heaters

Physical form: ① The appearance, condition, location, and anatomical

configuration of each component

38Topological links for DURESS II

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Exercising the WDAAH representation 의 가치는 다양한 links 에 의한

정보임– WD 를 control 할 때 고려해야 하는 특성들을 나타냄 – F → A :

• Temperature goal = energy and mass balance• Demand goal = mass balance

– A → G– G → P

These relationship should be considered by actors– How this representation of DURESS II can be used– To interpret verbal protocol (Vicente et al., 1995)– To simulate problem-solving trajectories (Bisantz and Vice

nte 1994)

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Exercising the WDAWork Domain Representation

– Quantitative, function-independent form by the equations (Table 6.3)→ Qualitative, function-oriented representation of the same relations

– 직관적으로 관계를 인식하기 용이함– 작업자들이 unanticipated event 에 대처하기

위해 활용가능

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Summary and implicationWork domain analysis is intended to identify the

information requirements associated with coping with unanticipated events

The concept of work domain can be analyzed using the abstraction-decomposition space as a modeling tool

The work domain representation can be used to address several design issues– The variables identified in the WDA help determine

what information needs to be measured and thus sensed.

– These variables also help determine what information needs to be derived by the use of models

– To help determine how all of this information can be organized into a database that supports goal-directed problem solving

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