Chapter 7 : Phase I : Work Domain Analysis

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Chapter 7 Phase I Work Domain Analysis

• ? ? ?

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Contents

1. Purpose
2. The importance of field descriptions
3. The abstraction-decomposition space
4. More about the abstraction hierarchy
5. Work domain analysis for process control
   micro-world
6. 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 Rasmussens(1979, 1985)
  abstraction-decomposition space WDA tool
• To explain the detailed AH
• To show an examples of how the abstraction-decompo
  sition 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
• ??? ??? ???? ??? Designer? Worker??? ???? ??? ?
• 3??? ???? Task Analysis? ?? ?? ?????? ????, ???
  ?? ???? ???? event-Independent representation ??
• Map ? Direction
• Work domain representation ? Task representation

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Simons parable about an ant(1981)

• ???? ??? ???? ??? ? ??? ????? ??
• ??? ??? constraints ??? constraints
• ???? ??? ??? ?? ??? ??
• The environment is relevantly invariant over
  particular initial conditions, task goals and
  trajectories
• ??? ??? ?? ????? ??? ??? ?? constraints? ?? ???,
  WD? ????(functional structure)? actor? action?
  constraints??.

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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

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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 task
• 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
Simons Parable Beach Ants actions
Mathematics Physics Field Dynamics Predict possibilities Possibilities for motion Structure Trajectory Kinematics Describe instances Motion Behavior
Automobile Driving Field of safe travel Drivers actions
Work Analysis Work domain Tasks
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The abstraction-decomposition space

• Rasmussen (1979, 1985)
• A two-dimensional modeling toll that can be used
  to conduct a work domain analysis
• ? section?? ? ?
• ??? abstraction-decomposition space? Field
  description?? ??? ? ????
• ?? ??? hierarchy? abstraction and decomposition
  hierarchy? ?? ???

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An example of ADS
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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

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An Example of ADS
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An example of ADS

• ??? ADS? ?? Trajectory? ??
• 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

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?? ?????? ???
Baseball Manager
Warmth
First-Base Coach
Third-Base Coach
Fireplace
Furnace
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?? ?????? ???

• ????? ???
• 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
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?? ?????? ???

• 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

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?? ?????? ???

• 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
Fireplace
Furnace
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Different MeanEnds 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
  actors action (Table 7.1 ??)
• 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

• 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

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Stratified Hierarchies

• The Ah belongs to the class of stratified
  hierarchies described by Mesarovic et al. (1970),
  
• The properties of which are listed here
• ?? ??? ?? ???? ?? ?? ??
• ? ?? ??? set of terms, concepts, and principles
  ???.
• ?? ???? ???? ?? ??? ??? ???, ??? ?? ??? ??? ???
  ?? ??? ??? ????.
• ?? ????? ????? ?? ??? ?? constraints?? ????, ???
  ??? ??? ?? ??? ?? ?? ??? ??? ?? ???
• ???? ?? ??? ??? ?? ??? ??? ????

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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

• 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 ??? ????? ?? ?? ?? ??

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Three goal-oriented questions Why? What? How?
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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

• 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

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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)
• 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

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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? ??? level ??? decompose
• P-W H ??
• To begin with the contents of the top level and
  the bottom two levels
• ??? ?? level ??
• ? Goal? ?? AH representation ? ? combine
• action means end ? structural means end ??

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Hints for conducting a WDA

• ? level? ?? nodes ? ?? modeling languages
• Why, what, how question ? ????? ??
• ?? type? Hierarchy ? ?? ?? ??
• Decomposion H? ?? ???? ?? object? ??? AH? ?? ????
  ?? object? functional description
• ? Your representation? ?? ? ?? ? ??
• ? ?? example ? ?? ??

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Summary
Build