SY DE 542

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SY DE 542
Basic Design of Info Reqts The Language of
Interface Design Jan. 24, 2005 R. Chow Email
chow_at_mie.utoronto.ca
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TA

• Munira Jessa
• Tel xtn 4904
• Email mnjessa_at_engmail
• Office E2 1303N (AIDL)
• Will grade Checkpoints 3,4,5 one of the two
  reports
• Between lectures, contact Munira FIRST for any
  course-related questions

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Case Study Apollo 13

• April 1970
• NASAs 3rd mission to carry humans to lunar
  surface
• Oxygen tank explosion
• Oxygen stores depleted within 3 hours loss of
  water, electricity, propulsion system
• Mission aborted but crew returned safely

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Apollo 13

• Mission controllers took 54 minutes before
  realizing that oxygen tank had exploded, and
  command module was dying
• Why??
• Look at snapshots of actual Mission Control
  screens and try to locate relevant data values
• (Woods, Patterson, Corban, in press)

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Apollo 13 Discussion

• Why was the explosion hard to spot?
• No History / Trend information
• Previous value
• Increase / decrease / constant
• Rate of Increase / decrease
• No Limits / Critical Values information
• Maximum allowable value
• Normal value

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Context

• A background for reading data
• Turns data into information (with meaning)
• Examples
• UV rating of 6
• Test score of 27
• Output temperature of 30 deg C (DURESS)

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Single Variable Constraints

• Start with list of variables for each AH level
• For each variable, ask
• What are the Limits? Min. / Max. / Both?
• What is High vs. Low?
• What is Good vs. Bad?
• What is Safe vs. Unsafe?

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Context (contd)

• Besides high vs. low, normal vs. abnormal
• Point where action can be taken
• Point where action will be taken (e.g., by
  automation)
• Point where action must be taken

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Design Implications

• Scale Ranges
• Alarm Limits
• Important Thresholds

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Redesigning Apollo 13 Displays
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Redesigning (contd)
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Redesigning (contd)
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Apollo 13 Discussion (contd)

• Why else was explosion hard to spot?
• Data overload
• Many data values
• Need for simultaneous monitoring
• Need for continuous monitoring
• Critical events may be of short duration

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Salience

• What stands out in an interface
• Consider what user needs first, second, third
• Direct attention accordingly

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Designing for Salience

• Colour
• Large size
• Centred
• Moving
• Flashing

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Salience (contd)

• What is more salient?
• Red or Grey?
• Neon Green or Dark Green?
• High-pitch or Low-pitch Sound?

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Salience Example 1
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Salience Example 2
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Salience (contd)

• Salience is relational
• Each new form added changes the salience of all
  others
• Direct attention, not monopolize
• Salience as a need, not as a rule

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Levels of Visual Information Representation

• Graphic Atoms
• Graphic Fragments
• Graphic Forms
• Views
• Workspaces
• (Woods, 1997)

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Graphic Atom

• Smallest unit
• A letter, digit, line, colour block
• Design decisions
• colour,
• size,
• shape,
• length,
• thickness,
• angle, etc.

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A
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Graphic Fragments

• Words, numbers, bars, scale, labels
• Design decisions
• position,
• content of numbers, words
• relation to near fragments, (proportion,
  salience)
• forms of reference

temperature
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Forms of Reference

• Different kinds of mappings between
• Visual Form
• what something looks like
• Representational Form
• how it conveys meaning about the world to a user

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Visual and Representational Form

• Visual Token (an atom or a fragment, etc.)
• has a visual form a representational form
• Visual Token
• Word e.g., Temperature
• Visual Form
• Black, Arial font, lines and curves
• Representational Form
• a variable, a measure of heat

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Forms of Reference

• 3 kinds
• 1) Propositional
• 2) Iconic
• 3) Analogical
• Describe how the visual token relates between the
  user and the world

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Propositional Form
tells
arbitrary
Observer
Token
World

• Relation between the token and the world is
  arbitrary
• Token tells the observer about the world
• Typically words, numbers, some graphics
• Relies on stored knowledge such as language,
  numbers
• Gives current state but little more

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Iconic Forms
recognizes
looks like
Observer
Token
World

• Depends on quality of visual form to look like
  the world
• Token should evoke recognition
• Relies on observer experience with the world
• Typical icons

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Analogical Forms
captures natural constraint
processes constraint
Observer
Token
World

• May or may not look like world
• Typically graphs on contextual backgrounds

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Examples

• Stop light

propositional
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Airline departure and arrival signs
iconic
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Stop Sign
propositional
STOP
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Stove Labels
REAR FRONT
propositional
iconic
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Mixed Forms of Reference

• Windows Recycle Bin
• Recycle Bin
• darkens/lightens
• fills/empties

• iconic
• propositional
• iconic

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Map

• Words
• Symbols
• Landmark Images
• Spacing and Scale

• Propositional
• Propositional
• Iconic
• Analogical

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Forms of Reference Summary

• Propositional and Iconic usually give 1 piece of
  information
• Analogical usually gives many pieces
• Representation is not right or wrong but changes
  the work of the observer

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Work involved in processing representations

• Analogical perceptual
• Propositional memory
• Iconic recognition memory
• (Propositional and Iconic both rely to some
  degree on knowledge in the head. Analogical
  leaves knowledge in the world.)

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Graphical Forms

• Graphs, Indicators
• Convey meaning
• Design decisions
• Analog or digital forms
• Context
• Salience

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Analog vs. Digital

• Digital
• uses propositional reference
• set of numerical strings that describe the
  referent e.g. 100.91
• observer reads the information

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Digital Forms

• often only current state is available
• very difficult to display history of the referent
• past or future states must be
• remembered
• calculated
• displayed separately
• memory and mental workload for user

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Design Requirements

• Label/Identifier
• The Value itself
• Precision ( of significant digits)
• Showing context
• Normal / Abnormal?
• Max / Min?
• Change?

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Showing Context with Digital Forms
Change the colour of the numbers for meaning e.g.
red for alarms
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Arrows to show rate and direction of change
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Ratios to show performance relative to a target
value
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C
Units also add context
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Analog

• uses analogical reference
• data is represented by a relationship between
  visual tokens on the screen
• representation is not as direct as digital
• requires the interpretation of a position in space

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Analog

• Relationship is typically between
• an indicator, and
• a reference scale
• Reference scale Frame of reference

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Aspects of Analog Forms

• Movement of the indicator is in space and
  relative to landmarks
• Landmarks are ticks, labels etc.
• Movement depends on the type and grain of the
  scale
• There are multiple possible frames of reference

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Frames of Reference
1-dimensional frame of reference
2-dimensional frame of reference
indicator
indicator
scale
scales
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Design Requirements

• Scale range (max, min, offscale, failed)
• Reference values
• Indicator, labels, scales

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Possible Reference Values

• 1. Value vs. its past values
• changes over time, rate of change
• 2. Value vs. its future values
• predicted values
• 3. Value vs. its target value (or range)
• Setpoints
• 4. Value vs. alarm limits/max/min values
• 5. Value vs. key decision points

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In terms of Workload

• Analog is generally easier for decisions made
  against a referent, done perceptually
• Digital requires mental comparisons and memory in
  this situation
• Digital needed when accuracy required

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The Principle of Primacy of Perception

• Whenever you can offload a mental task to a
  perceptual task you take advantage of human
  capabilities and make work easier.

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Analog ExamplePolar Star Display
Multiple scales put together
One scale
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Other Analog Forms

• Combined with digital

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Stacked Bar Graphs
- another example of multiple analog forms
v4
v3
v2
v1
Heightv1v2v3v4
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Icons that are Analog
Icon fills with water to show level
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More analog forms
Degree of rotation shows degree valve is open.
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Checkpoint 3 (due Jan.31)Information
Availability

• Extract a list of variables for each AH level
• For each variable, determine if it is
• Currently Available
• Directly sensed?
• Calculated from sensor data?
• Currently Unavailable
• Can be calculated from sensor data?
• Can be sensed? (If so, will sensor be added?)
• Cannot be sensed or calculated?
• (If so, using a heuristic/substitute measure?)
• Submit in Tabular format