1 Chapter 7 : Phase I : Work Domain Analysis 홍 승 권홍 승 권홍 승 권홍 승 권

2 Contents  Purpose  The importance of field descriptions  The abstraction-decomposition space  More about the abstraction hierarchy  Work domain analysis for process control micro-world  Summary and implications The

3 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

4 The importance of field descriptions Field Description = Work Domain Representation 시스템 안전을 위협하는 것들은 Designer 나 Worker 들에게 친숙하지 않았던 것 3 장에서 보았듯이 Task Analysis 가 이런 것을 충족 시켜주지 못하므로, 새로운 것에 대처하기 위해서 는 event-Independent representation 필요 –Map ← Direction –Work domain representation ← Task representation

5 Simon’s parable about an ant(1981) 기하학적 도형의 관점에서 보았을 때 개미의 이동 경로는 복잡 개미의 심리적 constraints + 해변의 constraints 행위자체 보다는 환경에 대한 이해가 중요 The environment is relevantly invariant over particular initial conditions, task goals and trajectories 해변의 구조가 어떤 상황에서도 개미의 행동에 대 한 constraints 가 되는 것처럼, WD 의 기능구조 (functional structure) 는 actor 의 action 에 constraints 이다.

6 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

7 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 task –The field describes constraints on action, not action itself

8 Field of safe travel

9 Comparison of various analogues used to show the difference between work domain and task analysis NavigationMapDirections Simon’s ParableBeachAnt’s actions Mathematics & Physics Field Dynamics Predict possibilities Possibilities for motion Structure Trajectory Kinematics Describe instances Motion Behavior Automobile DrivingField of safe travelDriver’s actions Work AnalysisWork domainTasks

10 The abstraction-decomposition space 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 ?

11 An example of ADS

12 An example of ADS A professional electronic technician engaged in troubleshooting computer equipment Each 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

14 An example of ADS 세가지 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 filed 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 actors have available for action

15 다른 계층구조와의 차이점 Car TireBattery Mammal DogCat Baseball Manager First-Base Coach Third-Base Coach Warmth FireplaceFurnace

다른 계층구조와의 차이점 계층구조의 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 차이점 Second 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 DogCat Car TireBattery

18 다른 계층구조와의 차이점 The 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 FireplaceFurnace

19 Different Mean–Ends Link Newell & 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.

20 More about the AH  To describe the generic properties of the AH  To review some evidence that the AH is a psychologically relevant way of describing complex STS.  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  To describe some hints for conducting work domain analysis

21 Stratified Hierarchies The Ah belongs to the class of stratified hierarchies 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 갖 는다. – 특정 시스템을 서술하기 위해 계층의 선정은 관측자, 그들 의 지식 그리고 시스템 통제에 대한 그들의 관심에 달려있 다. – 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 이동하 라

Five levels of constraints Functional PurposeDomain 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 functionsDescription 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

23 Psychological Relevance There are many different ways to represent a work domain –Algebraic and state equations From a psychological perspective, –One of the most important features of an AH is that higher levels are less detailed than lower levels 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 것만 찾음

Three goal-oriented questions: Why? What? How? Subjective Mental Workload NASA TLXSWAT Performance Reaction Time Error Paper Form StopwatchVideo Camera Computer Why ? How ? What ? Why ? How ? What ? Why ? How ? What ?

25 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

26 Coping With the Unanticipated A disturbance results in the breaking of one or more constraints that govern the work domain under normal circumstances 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

27 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) Can work domain analysis cope with the unanticipated? –Questions is not clearly answered by the “logic of analytical redundancy”. The issue lies in the system of analysis (clear in fws, but not clear in scientist example) Reply: that is why it is important to identify all of the goal-relevant constraints

28 Hints for conducting a WDA  Define a boundary  Use a matrix diagram as an overview of the various representation  To begin by constructing the part-whole Hierarchy  Action 이 가능한 level 까지만 decompose  P-W H 시작  To begin with the contents of the top level and the bottom two levels  가능한 많은 level 사용  각 Goal 을 위한 AH representation 그 후 combine  action means – end 와 structural means – end 염두

29 Hints for conducting a WDA  각 level 에 모든 nodes 는 같은 modeling languages  Why, what, how question 을 반복적으로 사용  다른 type 의 Hierarchy 가 들어 가지 않게  Decomposion H 를 따라 움직이면 다른 object 가 나오고 AH 를 따라 움지이면 같은 object 의 functional description ⑪ Your representation 을 여러 번 수정 및 반복 ⑫ 작은 example 을 참고 하라

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