Keeping Track: Coordinating Multiple Representations in Programming

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Keeping Track Coordinating Multiple
Representations in Programming

• Pablo Romero, Benedict du Boulay Rudi Lutz
• IDEAs Lab,
• Human Centred Technology Research Group,
• School of Science and Technology,
• University of Sussex.

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Background

• Computer programs can be looked at from different
  perspectives
• Experienced programmers mental representations
  include multiple perspectives and mappings
  between them
• SDEs often provide multiple, multimodal, linked
  and concurrent displays (code, visualisation(s),
  output)
• Programming requires co-ordination of these

BlueJ Java tutoring Environment Kolling
(2000) Monash University
3
Some Research Questions

• Are there patterns of interaction which
  characterise better debugging performance?
• Representation use (attention and switches)
• Tool use
• Are graphical representations more helpful than
  textual ones?
• Is debugging performance associated with any
  individual difference variable values?

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Contents

• Programming is a multi-representation and
  multi-faceted activity
• Debugging
• Experiments
• Static System
• Dynamic system
• Conclusions

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Representations - The Problem

• The original problem in real world terms
• The abstraction of the problem, in real world
  terms, but omitting irrelevant detail
• The realisation of the real world abstraction in
  terms of programming forms e.g. general
  computational methods of approach
• The detailed realisation of the program in terms
  of the kinds data-structures and algorithms
  available to be used in the given language

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Representations - The Code

• The code itself as data-structures and
  algorithms
• The input/output behaviour of the code when run
• Dynamic representations of different aspects of
  the code, e.g. control-flow and data-structure
  representations

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Representations - The Context

• The workings of the underlying virtual machine
• The workings of the programming environment
  itself
• Descriptions of the code produced by
  static/dynamic analysis tools

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Programming Skills Debugging

• Subdivision of the task
• Strategies for divide and conquer and for keeping
  track within and between representations
• Reasoning about overall strategy
• Reasoning in the problem and programming domains
• Forwards from code to behaviour, and backwards
  from behaviour to code
• Between representations
• Instrumenting the situation
• Tools for observing hidden events e.g. print
  statements

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Dynamic SDE experiment

• 42 participants (1st 2nd year ug)
• Verbal and graphical abilities pre-tests
• 5 programs
• 1 control,
• Graphical-textual visualisations,
• Control-flow, data structure errors
• 1 error each
• Static SDE with 4 windows
• Code
• Objects
• Call sequence
• Output
• Breakpoints

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The experimental tool

• Modified version of Restricted Focus Viewer
• Presents blurred image stimuli
• User moves unblurred foveal area around screen
• Logs user actions and records audio

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Experimental data

• Debugging performance
• Accuracy
• Spotting time
• Representation use
• Fixation periods
• Switching
• Individual differences
• (Verbal protocols)

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Debugging accuracy results
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Window fixation results
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Window switching results
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Window switching results
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Breakpoint fixation results
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Critical window fixation results
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Results summary

• Visualisations helpful
• More interaction for intermediates
• Graphical condition associated with more
  efficient use for best performers
• Positive correlation between graphical literacy
  and debugging accuracy

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Questions and Conclusions

• How far does window blurring alter programming
  strategy? e.g. Peripheral vision
• How far can we assume that the unblurred window
  is the focus of attention?
• How do we interpret time spent focusing on a
  representation? Utility vs. difficulty
• How do we interpret different patterns of
  switches? E.g. rapidly between a pair or reps.,
  leisurely between a pair of reps.
• Should we expect stronger interactions between
  graphical/spatial/textual abilities and
  representation preferences

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AcknowledgementsRichard CoxEPSRC
www.cogs.susx.ac.uk/projects/crusade/
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The End
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BlueJ Java tutoring Environment Kolling
(2000) Monash University
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Background

• Computer programs can be looked at from different
  perspectives
• Experienced programmers mental representations
  include multiple perspectives and mappings
  between them
• SDEs often provide multiple, multimodal, linked
  and concurrent displays (code, visualisation(s),
  output)
• Programming requires co-ordination of these

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Some of the Tasks.

• Understanding the problem
• Constructing general approach
• Specifying sequences, entities and relationships
• Coding
• Debugging (at any of the above stages)
• Maintenance

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Static SDE experiment

• 48 participants (1st 2nd year UG)
• Verbal and spatial abilities pre-tests
• 4 programs to debug
• 4 errors each
• Static SDE with 3 windows
• Code
• Visualisation
• Output

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Debugging strategy results

• Qualitative analysis for 2 contrasting
  participants
• Experience
• Verbal ability
• Initial code browsing episode
• Two ways of detecting bugs
• by spotting something odd in code browsing
  episode
• by coordinating representations

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Window fixation results

• Poor performers focus on the code a lot
• Good performers also focus on objects window

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Visualisations
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Sample class of DrinkMachine program
buggy output
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Representation Issues.

• Cognitive
• Relationships between internal and external
  representations
• Structure of knowledge and nature of expertise
• Educational
• Evolution of knowledge and its organization from
  novice to expert
• Activities to support learning
• Scaffolding needed at various stages
• Aesthetic and Motivational
• Nature of the experience
• Quality of the artifacts

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Crusade overall aims

• Investigate the co-ordination of multiple
  external representations in OO program
  comprehension
• Investigate role of perspective, modality and
  individual differences in representation
  co-ordination in programming.
• Develop set of design principles for program
  comprehension tools
• Develop computerised experimental tool to study
  representation co-ordination in programming