Human Computer Interaction

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Human Computer Interaction
?? 10 Models of the User

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Types of users

• Requirement models
• Establish users needs
• Socio-technical models
• Soft system models
• Participatory design models
• Cognitive models
• Represent users of interactive systems
• Hierarchical models
• Linguistic models
• Physical device models
• Cognitive architecture

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Socio-technical model

• Basic assumptions
• Technology is developed as part of a wider
  organizational environment.
• Important to consider social and technical issues
  side by side.
• Different approaches
• USTM/CUSTOM
• focuses on establishing stakeholder requirements
• OSTA
• describe what happens when a technical system is
  introduced into an organizational work
  environment
• ETHICS
• address the social and the technical design using
  different design teams

4
Soft system model

• Principle
• The organization as a system of which the
  technology and people are components.
• Focus on understanding the situation rather than
  on devising a solution.
• Procedure
• Develop a rich picture
• description of the problem situation
• Generate root definition
• Clients, Actors, Transformation, Weltanschauung,
  Owner, Environment.
• Devise a conceptual model
• what the system has to do to fulfill the root
  definition
• Compare the actual system with the conceptual
  model

5
Participatory design

• Principles
• users are experts in the work context
• a design can only be effective within that
  context if these experts are allowed to
  contribute actively to the design
• Features
• context or work oriented
• collaboration between the user and designers
• iterative approach
• Methods
• brain-storming
• storyboarding
• workshops
• pencil and paper exercise

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Goal and task hierarchy

• Types
• GOMS
• CCT
• Issue
• Granularity
• where do we stop decomposing tasks
• where do we start our analyses at different
  points in the hierarchy of goals
• Different design issues demand different levels
  of analysis
• Error
• what can it say about difficulties the user may
  have along the way

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GOMS

• Good for describing how experts perform routine
  tasks.
• Goals
• Operators
• lowest level of analysis
• There is still a degree of flexibility about the
  granularity.
• Methods
• sequence of operators to achieve subgoals.
• Selections
• depends on the particular user and the state of
  the system.

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CCT

• Goal
• Measure the complexity of an interface
• The more production rules, the more difficult the
  interface is to learn
• Two parallel description
• users goal as production rules
• If . Then .
• systems grammar as generalized transition
  networks.
• Both of them can be represented as hierarchies
  and compared to find mismatches and to produce a
  measure of dissonance
• One can predict the difficulty of the mapping
  between the users goals and the system model
• Too much work even for a part of an interface

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Linguistic models

• To understand the users behaviour and analyze
  the cognitive difficulty of the interface.
• BNF
• It views the dialog at a purely syntactic level.
• Complexity as the number of rules or the number
  of sequence and choice.
• Task Action Grammar
• emphasize consistency using parameterized grammar
• encode the users world knowledge.

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Display based systems

• Problems of Goal hierarchy
• They largely ignore system output
• assume that the users know exactly what they want
  to do and execute the appropriate command
  sequences blindly.
• More display oriented systems encourage less
  structured methods for goal achievement
• such recognition based searching is extremely
  difficult to represent as a goal structure.

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Keystroke level model

• Unit tasks within interaction
• the execution of simple command structure
  sequences
• typically taking no more than 20 seconds
• no high level mental activity
• can be thought of as a very low level GOMS model
  where the method is given.
• Five different physical motor operators
• K(keystroking), B(pressing), P(Pointing),
  H(Homing), D(Drawing).
• Give accurate quantitative predictions about
  performance
• But the range of applications is very small.

12
Problem Space Model

• To model a knowledge level activity
• A system exhibiting rational behavior.
• A sequence of environment and agent states as
  they progress in time.
• A problem space represents a goal by defining the
  desired states as a subset of all possible states
• Four different activities that can occur within a
  problem space
• Goal formulation, operation selection, operation
  application, and goal completion.
• Evolution of problem spaces as a stack-like
  structure
• new spaces being invoked and placed on the
  problem space stack only to be popped off the
  stack once they achieve their goal.

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Class projects

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• Task Model
• User Model
• System Model