1 / 26

Chapter 3 : Normative Approaches “ The one best way ”

Chapter 3 : Normative Approaches “ The one best way ”. 홍 승 권. Three Generations of Work Analysis Methods (Rasmussen 1997). Normative models : how a system should behave Tayloristic work methods analysis, traditional task analysis, GOMS analysis

feryal
Download Presentation

Chapter 3 : Normative Approaches “ The one best way ”

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Chapter 3 : Normative Approaches“The one best way” 홍 승 권

  2. Three Generations of Work Analysis Methods (Rasmussen 1997) • Normative models : how a system should behave • Tayloristic work methods analysis, traditional task analysis, GOMS analysis • Descriptive models : how a system actually behaves in practice • Critics from anthropological, activity theory and naturalistic decision making communities • The assumptions they make about human work are not realistic and not very useful • There are problems in deriving implications for design from descriptive work analysis techniques

  3. Three Generations of Work Analysis Methods (Rasmussen 1997) • Formative models : Requirements that must be satisfied so that the system could behave in a new, desired way. • To help us specify the design attributes that computer-based information systems should have to satisfy

  4. Normative Approach : Task Analysis • Definitions • To examine “ the tasks that must be performed by users when they interact with systems” • The study of what an operator is required to do in terms of actions and/or cognitive processes to achieve a system goal • One best way • For identifying the ideal ways in which the job should be performed

  5. Three levels of task analysis techniques • Level 1 : input-output • Identify inputs, outputs, and constraints • Constraints that must be taken into account in selecting the actions • Ex) Rate of gasoline consumption • Two relevant constraints : the number of kilometers in a mile and the number of liters in a gallon • Several different set of actions • Using a calculator : Reading → Typing into the calculator • Using metal arithmetic :

  6. INPUTS OUTPUTS Task Miles traveled since last fill-up Automobile gas consumption rate in Km/L Gallons at this fill-up CONSTRAINTS : 1 Mile = 1.609 km 1 Gallon = 3.785 Liters Rate of gasoline consumption in an automobile

  7. Level 1 : input-output • A very high level product description of the task • 행위에 대한 constraint는 다른 형태일 수 있다. 연료소비의 예에서는 변수들 사이의 관계였다. Constraint는 어떤 순차적 절차일 수도 있다. • 이들 constraint를 고려하지 않고 정확히 작업을 수행하는 것은 불가능하다. 그러나 작업이 실제 어떻게 수행되는 것과는 독립적이다. • Constraint 들은 문제상태공간을 줄이는 기능을 한다. 그러나 단일 행동절차를 지적하지는 않는다. 단지 가능한 행위 절차의 선택폭(자유도)을 제한한다.

  8. Level 2 : Sequential Flow • To identify ordered sequence of actions • Flowchart of the process that workers should follow to perform the task. • Ex) Rate of gasoline consumption • Read current odometer value • Read odometer value at last fill-up • Calculate the difference to obtain miles traveled since last fill-up • EX) Fig 3.2 • This level of task analysis is usually dependent to the device workers currently have available to perform the task • If you had a trip odometer, --- just read

  9. Level 3 : Timeline • To identify ordered sequence of actions with duration estimates for each action • The most detailed of all • Ex) Rate of gasoline consumption • 0-1 s: Read current odometer value • 1-2 s: Read odometer value at last fill-up • 2-3 s : Calculate the difference …. • Ex) Fig. 3.3 • Only one right way to perform this task • All of the discretion has been eliminated.

  10. Goal Goal Goal Constraints VS Instructions(Three levels of task analysis) Level 1 : Input-output Level 2 : Flow Sequence Level 3 : Timeline

  11. Implications • Different forms of work analysis make different assumptions about the nature of work • So they lead to different designs, which in turn, lead to different types of guidance to workers.

  12. Constraints VS Instructions

  13. Conclusions • Several advantages of constraint-based approach • More discretion • Greater variability in action • Fewer assumptions about the properties of the device • It is more likely that the new design will result in new functional possibilities, • rather than being constrained by designer’s current assumptions about functionality • Task-artifact cycle : Instruction-based approach의 단점 • 두 가지 접근방법의 장점을 활용하자

  14. + Error Action Output Goal Worker Plant - The view from control theory • To understand goal-oriented behavior, using control theory • In a conceptual level A simple model of goal-directed behavior Goal (g), Output (o), Error (e), Action (a) Control strategy by the worker (W), dynamics of the plant (P)

  15. A simple model of goal-directed behavior • 관계식 • action(a) = strategy(W) * error(e) • error (e) = goal state(g) – output(o) • a= w(g-o) • 만약 (w, g, o)를 안다면, action sequence를 예상할 수 있다. (초기상태 t=0, g=o) • 초기상태가 알려지지 않으면, action을 예측하지 못함. • 만약 W가 불확실하면, action을 예측하지 못함.(STS 에서 여러 가지 전략 가능)

  16. Disturbance + Error Output State Action Goal Worker Plant - A complex model of goal-directed behavior A complex model of goal-directed behavior • Disturbance (d) : • Factors that affect the state of the plant in ways that have not been or can not be, anticipated by system designer

  17. A complex model of goal-directed behavior • 관계식 • a=(g-d) / P • d의 예측이 불가능하므로, a 의 예측은 불가능 • 동일 목표를 위해 다른 행위 가능, 같은 행위가 다른 시간에 다른 영향을 줌 • Context-conditioned variability (motor control) • Unanticipated variability (cognitive engineering) • Situated action (cognitive science)

  18. Resolution(Closed/Open systems) • The more closed a system is, the more amenable it is to instruction-based forms of task analysis. • Open system gives rise to context-conditioned variability • Workers must adapt online in real time to disturbance that cannot possible be foreseen by analysts (Hirschhorn 1984). • 참고문헌 : 사전에 예측불가: Ujita, Kawano & Yoshimura, 1995)

  19. Constraint-based approaches • Negative feedback models : constraint-based structure, not instruction-based • Discretion is not the same as complete freedom • Not advocating that workers be allowed to do whatever they want • The discretion and flexibility that we advocating is bounded by constraints.

  20. An unresolved problem • Constraint-based task analysis can lead to new design functionality, making it more likely that productivity will be improved. • A particular goal to be achieved may not be identifiable beforehand : an unanticipated emergency in a nuclear power plant. • CBTA의 한계 → Work Domain Analysis로 극복

  21. An unresolved problem • How can we know what the goal should be? • To require workers to “Note any problems” by Shepherd(1992) • It merely provides a place holder for what workers are supposed to do • Little to identify the information or knowledge that workers require to cope with • Even constraint-based task analysis do not provide a very satisfactory basis for dealing with unanticipated events.

  22. Dealing with unanticipated events • Ex) Spatial navigation (Thorndyke and Goldin 1983) • How people learned to find their way • Two types of spatial knowledge • Procedural knowledge : sequence of actions • Survey knowledge ; spatial relationships between locations and routes in an environment • Navigation aids • Procedural knowledge can be embedded in directions • Survey knowledge can be embedded in a map

  23. Dealing with unanticipated events • Direction 과 Map의 장단점

  24. Relevance to work analysis • Two forms of work analysis • Task representations (like directions) • What goals they should achieve or how they should be achieving them • Work domain representations (like maps) • To describe the structure of the controlled system • Task VS Work domain • Task : what workers do • Work domain : what workers do it on (i.e., the object of action) ★ Those familiar with computer programming - Control structure : task - Data structure : work domain

  25. Task analysis VS Work domain analysis

  26. Summary • Most existing task analysis techniques are not very useful • Instruction based TA • Not suited for complex STS • To underestimate context-conditioned variability • Constrained based task analysis are better suited for complex STS • Contribute in flexibility, productivity, worker health and on-the-job training • But not capable of dealing with unanticipated events • Work Domain Analysis for unanticipated events • Work domain analysis + Constrained based task analysis

More Related