errors -...
TRANSCRIPT
Fall 2017 PSYCH / CS 6755 2
Agenda
ØError typesØSlip typesØError prevention guidelinesØError recovery guidelines
Fall 2017 PSYCH / CS 6755 3
Error-handling Strategies
1. Avoid and prevent
2. Identify and understand
3. Handle and recover
Fall 2017 PSYCH / CS 6755 4
Perceptual Errors
ØResult from poor perceptual cuesv Display of objects that are visually similarv Invisible or poorly expressed statesv Failure to capture user’s attentionv Lack of perceivable feedback
Fall 2017 PSYCH / CS 6755 6
Cognitive Errors
ØCaused by taxing memory and thinkingv Tax recall memoryv Poor mnemonic aidsv Inconsistencyv Lack of context or status info
• e.g., where came from in a menuv Mental calculations and translations
Fall 2017 PSYCH / CS 6755 8
Motor Errors
ØTaxing the motor skillsv Awkward movementsv Highly similar motor sequences
• e.g., double click, clickv Pressure for speedv Require a high degree of hand-eye
coordinationv Requiring special types of motor skills (type)
Fall 2017 PSYCH / CS 6755 10
Slips
ØAutomatic (subconscious) error that occurs without deliberation
ØExamples?
Fall 2017 PSYCH / CS 6755 11
Types of Slips
Ø1. Capture errorv Continue frequently done activity instead of
intended one• Type “animation” instead of animate• Confirm deletion of file instead of cancel
Ø2. Description errorv Intended action has much in common with
others possible (usually when distracted, close proximity)• ctrl key & caps lock key / Sun & Mac
Fall 2017 PSYCH / CS 6755 12
Types of Slips
Ø3. Data driven errorv Triggered by arrival of sensory info which
intrudes into normal action• Call to give someone a number, dial that number
instead
Ø4. Associative activationv Internal thoughts and associations trigger
action• Phone rings, yell “come in”
Fall 2017 PSYCH / CS 6755 13
Types of Slips
Ø5. Loss of activationv Forgetting goal in middle of sequence of
actions• Start going into room, then forget why you’re
going there
Ø6. Mode errorsv Do action in one mode thinking you’re in
another• Delete file, but you’re in wrong directory
Fall 2017 PSYCH / CS 6755 14
Error Prevention Guidelines
ØEliminate modes or provide visible cues for modes
ØUse good coding techniques (color, style)ØMaximize recognition, minimize recallØDesign non-similar motor sequences or
commandsØMinimize need for typing
Fall 2017 PSYCH / CS 6755 15
Error Prevention Guidelines
ØTest and monitor for errors and engineer them out
ØAllow reconsideration of action by user (e.g., removing file from trash)
Fall 2017 PSYCH / CS 6755 16
Error Recovery Guidelines
ØProvide appropriate type of feedbackv Gag - Prevent user from continuing
• Erroneous loginv Warn - Warn user an unusual situation is
occurring• Bell or alert box
v Nothing - Just don’t do anything (Careful, user must determine problem)• Mac: move file to bad place
Fall 2017 PSYCH / CS 6755 17
Error Recovery Guidelines
ØResponses (continued)v Self-correct - Guess correct action & do it
• Spell-check correctionv Dialog - System opens dialog with user
• Go into debugger on run-time crash
ØQuery - Ask user what should’ve been done, then allow error action as legal one
• Command language naming error
Fall 2017 PSYCH / CS 6755 18
Error Recovery Guidelines
ØProvide undo functionØProvide cancel function from operations in
progressØRequire confirmation for drastic,
destructive commandsØProvide reasonableness checks on input
datav Did you really mean to order 5000?
Fall 2017 PSYCH / CS 6755 19
Error Recovery Guidelines
ØReturn cursor to error field, allow fixv Tell them what to fix, how to fix it
ØProvide some intelligencev Guess what they wanted to do
ØProvide quick access to context-sensitive help
Fall 2017 PSYCH / CS 6755 20
Error Handling Example (Web)
ØForm fill in is the most common error case