1. SY DE 542 Basic Design of Info Req’ts The Language of Interface Design
Jan. 24, 2005
R. Chow

2. TA Munira Jessa Tel: xtn 4904
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

3. Case Study: Apollo 13 April 1970
NASA’s 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
April 10, 1970, NASA launched Apollo 13 mission - intended to be 3rd mission to carry humans to the lunar surface
April 14, an explosion in one of the oxygen tanks caused damage to other systems, making it necessary to abort mission.
When Oxygen Tank # 2 exploded, Oxygen #1 was also damaged. All oxygen stores were depleted within 3 hours, along with loss of water, electrical power, and use of propulsion system. Command Module became unstable and had to be powered down.
Crew had to be transferred over to lunar module, and they were returned to earth safely on April 17.
Psi= pounds per square inch

4. 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)

9. 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

10. 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)

11. 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?

12. Context (cont’d) 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

13. Design Implications
Scale Ranges
Alarm Limits
Important Thresholds

14. Redesigning Apollo 13 Displays

15. Redesigning (cont’d)

16. Redesigning (cont’d)

17. Apollo 13 Discussion (cont’d)
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

18. Salience What “stands out” in an interface
Consider what user needs first, second, third …
Direct attention accordingly

19. Designing for Salience
Colour
Large size
Centred
Moving
Flashing

20. Salience (cont’d) What is more salient? Red or Grey?
Neon Green or Dark Green?
High-pitch or Low-pitch Sound?

21. Salience: Example 1

22. Salience: Example 2

23. Salience (cont’d) 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

24. Levels of Visual Information Representation
Graphic Atoms
Graphic Fragments
Graphic Forms
Views
Workspaces
(Woods, 1997)

25. Graphic Atom Smallest unit A letter, digit, line, colour block
Design decisions:
colour,
size,
shape,
length,
thickness,
angle, etc. 3 A

26. Graphic Fragments Words, numbers, bars, scale, labels
Design decisions:
position,
content of numbers, words
relation to near fragments, (proportion, salience)
forms of reference
temperature

27. 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

28. 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

29. Forms of Reference 3 kinds 1) Propositional 2) Iconic 3) Analogical
Describe how the visual token relates between the user and the world

30. 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

31. Iconic Forms Depends on quality of visual form to look like the world
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”

32. Analogical Forms May or may not look like world
captures natural constraint
processes constraint
Observer
Token
World
May or may not look like world
Typically graphs on contextual backgrounds

33. Examples
Stop light
propositional

34. Airline departure and arrival signs
iconic

35. Stop Sign
propositional
STOP

36. Stove Labels
“REAR”
“FRONT”
propositional
iconic

37. Mixed Forms of Reference
Windows Recycle Bin
Recycle Bin
darkens/lightens
fills/empties
iconic
propositional

39. Map Words Symbols Landmark Images Spacing and Scale Propositional
Iconic
Analogical

40. 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

41. 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.)

42. Graphical Forms Graphs, Indicators Convey meaning Design decisions:
Analog or digital forms
Context
Salience

43. Analog vs. Digital Digital: uses propositional reference
set of numerical strings that describe the referent e.g
observer reads the information

44. 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

45. Design Requirements Label/Identifier The Value itself
Precision (# of significant digits)
Showing context
Normal / Abnormal?
Max / Min?
Change?

46. Showing Context with Digital Forms
123.45
Change the colour of the numbers for meaning e.g. red for alarms
123.45
Arrows to show rate and direction of change
123.45
123.45
Ratios to show performance relative to a target value
150.55
123.45 C
Units also add context

47. 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

48. Analog Relationship is typically between:
an indicator, and
a reference scale
Reference scale = Frame of reference

49. 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

50. Frames of Reference 1-dimensional frame of reference
indicator
indicator
scale
scales

51. Design Requirements Scale range (max, min, offscale, failed)
Reference values
Indicator, labels, scales

52. 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

53. 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

54. 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.

55. Analog Example: Polar Star Display
Multiple scales put together
One scale
scale
Current value
High limit
Low limit

56. Other Analog Forms
Combined with digital

57. Stacked Bar Graphs - another example of multiple analog forms v4 v3 v2
Height=v1+v2+v3+v4

58. “Icons” that are Analog
Icon “fills” with water to show level

59. More analog forms
Degree of rotation shows degree valve is open.

60. 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