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Chapter 9 Phase 3 : Strategies Analysis

Chapter 9 Phase 3 : Strategies Analysis. 홍 승 권. Purpose. Control task analysis 에서 분석된 활동을 수행하는 여러 가지 방법들을 이해하는 것 ( 즉 How 에 관심 ) Modeling tool = information flow maps. Control Task Analysis 와 Strategy Analysis 의 관계. CTA 와 SA 는 모두 action 측면을 다룬다 .

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Chapter 9 Phase 3 : Strategies Analysis

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  1. Chapter 9Phase 3 : Strategies Analysis 홍 승 권

  2. Purpose • Control task analysis에서 분석된 활동을 수행하는 여러 가지 방법들을 이해하는 것 (즉 How에 관심) • Modeling tool = information flow maps

  3. Control Task Analysis와 Strategy Analysis의 관계 • CTA와 SA는 모두 action 측면을 다룬다. • 그러나 CTA는 product description(무엇이 수행되는가) • y=f(x)에서 이 함수와 관련된 constraints를 찾는 것. • SA는 process description(어떻게 수행되는가?) • y=f(x)는 여러 가지 방법으로 수행됨

  4. Control Task Analysis : x f() y Information- Processing Activity Outputs Inputs Constraints y= f(x) Decision ladder의 한 box Strategies Analysis : x f() y Strategy A Outputs Inputs Strategy B Strategy C

  5. Multiple strategies for air traffic control • Work domain constraints • 공항주위와 공항내의 지리적 특성 • 통제될 필요가 있는 다른 비행기들의 특성 • Control task constraints • 동일공간에서 비행기간의 이격거리 • WD와 CT constraints가 고정된 상태에서 많은 전략이 가능 • 주어진 상황에 따라 어떤 Operating procedure가 더 경제적일까? • Work load가 적은 strategy 찾기

  6. Overload Threshold Cognitive Load Sa Sb Sc Task Demands FIG. 9.2. Adaptive regulation of cognitive load via the use of successively less demanding strategies (Sa, Sb, Sc) by air traffic controllers (adapted from sperandio, 1978)

  7. 사용하는 전략과 교훈 • 사용하는 전략들 • 항공기 1-3대: 각 항공기의 최적항로까지 계산 (based on speed, course altitude) • 항공기 4-6대: uniform speeds와 stereotypical flight path채택 • 항공기 6대 이상: 주 관심은 효율보다 안전. Waiting buffer를 만듬. • 교훈 • ATC display가 비행기 대수에 따라 자동으로 재구성될 수 있음. • 비행기 수가 적어도 ATC에 부담을 주는 경우도 있다 • 개별 ATC에 따라 다르고, 심지어 날짜에 따라 다르다. • 전략전환 가능 • 각 전략은 다른 수행기준을 갖고, 다른 정보지원을 요구함 • 전략이 바뀌는 시점예측 어려움

  8. 전략이란? • 전략은 a sequence of operation • A category of procedure • Instance of a procedure (X) • 예상치 못한 사건 때문에 하나의 범주로 정의하는 것이 효과적임 ♣ Flexible computer based information system 설계 가능

  9. a) Strategies as categories : Strategy A Strategy B Strategy C b) Action sequence as switching between instantiated strategies : Starting Point Ending Point A B C

  10. c) Timeline of action sequence : C Action Sequence B A Time FIG. 9.3. An illustration of the difference between defining a strategy as a category (Rasmussen, 1981) or as an exemplar of action sequence (Pay et l.,1993).

  11. Information flow mapsin electronic equip. failure • IFM은 다른 툴과 같이 완성된 것이 아님 • Not generic tool • Engineer VS Technician approach

  12. A Comparison of the Engineer’s and Technicians’ Troubleshooting Approaches in Terms of different Performance Criteria Which one is better?

  13. Diagnostic strategies • Topographic search와 symptomatic search • Topographic search (topographical location 이용) • To require a model of the normal state of the equipment (중앙부) • A location for the next observation is selected • Good0-bad judgment …. • Symptomatic search (information content 이용) • Pattern recognition • Decision table • Hypothesis and test

  14. Physical Model Reference Date in Diagram Tactical Rules of Search Find Location in System Recall or Read Diagram Model Of Normal Function Selection Of Next Location Good-bad Map of System Functional field Causal Path Find Causal Path or Funtional Fields Deduce Reference Data Good-Bad Judgment Fields Model of Physical Process Used only if reference Data are not Immediately available Failed system FIG. 9.4. Information flow map for topographic search strategy.

  15. Date-Driven Pattern Recognition Labeled in Terms of Cause, State, Event, Task, or Other Empirical Label Failed system FIG. 9.5. Information flow map for pattern recognition strategy.

  16. Label of Reference in Terms of Cause, State, Event, Task, etc. FOUND YES Pattern Matching Library of Failed State Symptoms Reference symptom Pattern Scan and Select Failed system MATCH? Tactical Rules for Selection of Next Entry to Test NO FIG. 9.6. Information flow map for decision table search strategy.

  17. Fault FOUND YES Present Operational Input Pattern Matching Deduce Response Pattern Reference Symptom Pattern MATCH? Failed system Model of Function in Hypothetical Failed State NO Search Strategy Next Hypothesis Hypothesis Of Fault in System Model Of Normal Function Tactical Rules for Selection of Next Entry to Test Hypothesis From Other Sources FIG. 9.7. Information flow map for hypothesis and test search strategy.

  18. A Comparison of the Resource Requirements of the Various Diagnostic Search strategies Identified by Rasmussen(1981)

  19. Design Implications • 전략은 actor-independent 하다. • Fig 9.9는 automation과 worker 에게 분배되었을 경우 • 자원요구(resource requirements)는 전략의 성격이다. • 예를 들어, Hypothesis and test search strategy는 장비에 대한 지식이 많아야 하고, 기억부담이 크며, complex reasoning이 요구된다. • 현재 사용되는 것이 아니라 사용될 수 있는 것

  20. Worker Automation Pattern Matching MATCH? Search Strategy Next Hypothesis Fault Found YES Present Operational Input Reference Symptom Pattern Deduce Response Pattern Failed System Model of Function in Hypothetical Failed State NO NO Hypothesis Of Fault in System Model Of Normal Function Modify the Model of Function According to Hypothesis Hypothesis from Other Sources Worker Automation

  21. Where do strategies come from? • Descriptive field study • The obtained data provide a basis for formative modeling of CWA • To determine what strategies could be used, and the performance criteria and subjective task formulation exhibited by workers • A priori analysis • To identify the possibilities for action by work domain analysis and control task analysis • Operation research methods • Dessouky et al (1995)

  22. Process Control Microworld의 전략분석 • Control Task Analysis 에서 도출된 6개 활동 중 1개 • formulation procedure • Pumps is nondiscretionary (Valve의 사용에 대한 분석 만) • There is a infinite set of component settings that will achieve the desired values • In other words, the actor has degrees of freedom available in choosing how to accomplish the task Desired Valve & Pump Settings Desired Inflow Rates (MI1, MI2) Configure FWSs Constraints

  23. f ( ) x y Single FWS Desired Inflow Rates (MI1,MI2) Desired Valve Settings Decoupled FWS Full FWS 3가지 전략들 • Single : uses only one of the two FWSs and thus three input valves. • Decoupled : Uses both FWSs but only four of the input valves. • Full : Uses both FWSs and five or six of the input valves.

  24. Functional Model VA1 VA Select 3 Valve Settings VA2 Detamine2 Secondary Valve Flows MI1 MI2 3 Valve Settings R1 Physical & Functional Models Topological Model Choose a FWS VB1 VB R2 VB2 Single

  25. VA1 VA VA2 R1 VB1 VB R2 VB2 Functional Model Functional Model 2Valve Settings Select 2 Valve Settings Determine 1 Secondary Valve Flow Select 2 Valve Settings 2 Valve Settings Determine 1 Secondary Valve Flow MI2 MI1 Physical & Functional Model Physical & Functional Models Topological Model Choose a Path Decoupled

  26. VA1 VA Functional Model Select 3(or 2) FWS A Valve Settings VA2 R1 VB1 5 or 6 Valve Settings VB MI1 MI2 Determine3 or 4 Secondary Valve Flows Physical & Functional Models R2 VB2 Topological Model Choose 5 or 6 Valves Select 3 (or 2) FWS B Valve Settings Full

  27. A comparison of the FWS Configuration Strategies in Terms of Different Performance Criteria

  28. 전략비교 설명자료 • 용량한계: 각 pump는 초당 10unit/sec. 가 한계 • Single은 총 10unit이하 • Decupled는 각각 MI1, MI2 10unit 이하 • Full은 MI1, MI2 합이 20unit이하 • Demand 변화에 따른 reconfiguration의 가능성 • 주요 결함에 대한 대처능력 (c.g. 다른 밸브사용) • 요구 기억부담 • 계산 요구 (one-to-many, one-to-one, many-to-many)

  29. A few general points • 표준화되지 않은 modeling tool (information flow map) • Strategies are categories • No specific valve settings are listed in the information flow map • No specific flow paths … • Not strictly follow one strategy • Switching between strategies to keep their work load at a manageable level • The same strategy can be used in different contexts

  30. Summary and implication • Strategies Analysis : Third phase of CWA • Objective of a Strategies Analysis • To identify the requirements that can lead to the design of a support system with flexible strategy switching. • The findings of Sperandio (1978) • ATCs changed theirs strategies to keep their work load at a manageable level • A computer-based information systems should support these opportunistic actions • How a strategies analysis for library information retrieval (Ch 12) • To present different dialogue modes for different strategies

  31. Summary Cognitive Work Analysis Framework Cognitive Work Analysis Systems Design Identify Realize Form Build Develop Models of Intrinsic Work Constraints Conceptual Distinctions Modeling Tools 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 v Information Flow Map 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

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