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Analysis and Validation - Lecture 4 - Information Visualisation (4019538FNR)

Analysis and Validation - Lecture 4 - Information Visualisation (4019538FNR)

This lecture forms part of the course Information Visualisation given at the Vrije Universiteit Brussel.

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Beat Signer
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March 06, 2021
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  1. 2 December 2005 Information Visualisation Analysis and Validation Prof. Beat

    Signer Department of Computer Science Vrije Universiteit Brussel beatsigner.com
  2. Beat Signer - Department of Computer Science - bsigner@vub.ac.be 2

    March 4, 2021 Four Nested Levels of Vis Design
  3. Beat Signer - Department of Computer Science - bsigner@vub.ac.be 3

    March 4, 2021 Validation ▪ Huge vis design space and most designs are ineffective ▪ Validate choices right from the beginning of the design process ▪ top-down design (problem-driven work) - start at top situation domain level - major challenge at data/task abstraction; mainly use existing idioms ▪ bottom up design (technique-driven work) - invention of new idioms or algorithms ▪ Validate all four levels of the design ▪ domain validation ▪ abstraction validation (what and why) ▪ idiom validation (how) ▪ algorithm validation
  4. Beat Signer - Department of Computer Science - bsigner@vub.ac.be 4

    March 4, 2021 Four Nested Levels of Vis Design ▪ Output from upstream level is input to downstream level ▪ errors at upstream levels cascade to downstream levels ▪ highly iterative design process
  5. Beat Signer - Department of Computer Science - bsigner@vub.ac.be 5

    March 4, 2021 Domain Situation ▪ A domain situation is defined by ▪ target users ▪ domain of interest of target users ▪ data of target users ▪ questions (tasks) of target users ▪ Outcome of design process ▪ understanding of user needs (user-centred design) - e.g. via observations or interviews ▪ Challenges and risks ▪ users can often not clearly specify their analysis needs ▪ designers make assumptions (rather than engaging with users)
  6. Beat Signer - Department of Computer Science - bsigner@vub.ac.be 6

    March 4, 2021 Data & Task Abstraction ▪ Abstract from answers to domain-specific questions at upstream to a generic representation ▪ questions from different domain situations can map to same abstract vis tasks - e.g. browsing, comparing or summarising ▪ Design abstract data ▪ data from upstream is often transformed to something different ▪ determine which data type supports a visual representation that addresses a user's problem
  7. Beat Signer - Department of Computer Science - bsigner@vub.ac.be 7

    March 4, 2021 Visual Encoding & Interaction Idiom ▪ Specific way (idiom) to create and manipulate the visual representation of abstract data ▪ visual encoding idiom - create a "picture" out of the data (what do users see?) ▪ interaction idiom - how do users change what they see? ▪ Design space of the combination of visual encoding and interaction idioms is very large ▪ data and task abstractions help to reduce the number of potential visual encoding and interaction idioms ▪ decision about good or bad matches based on human abilities (visual perception and memory)
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    March 4, 2021 Word Tree Example
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    March 4, 2021 Algorithm ▪ Implementation of visual encoding and interaction idioms ▪ can design different algorithms to realise the same idiom ▪ Various factors might impact the choice of a specific algorithm ▪ computational complexity (performance) ▪ memory usage ▪ level of match with visual encoding idiom ▪ Separate algorithm design (computational issues) from idiom design (human perception issues)
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    March 4, 2021 Threats to Validity ▪ Each design level has their own threats to validity ▪ wrong problem, wrong abstraction, wrong idiom or wrong algorithm
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    March 4, 2021 Validation Approaches
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    March 4, 2021 Validation Approaches … ▪ Can perform an immediate or downstream validation ▪ downstream dependencies add to the difficulty of validation - e.g. poor algorithm design may cause doubt when testing interaction technique ▪ use of mockups for early downstream evaluation ▪ Mismatches ▪ mismatch between the level at which the benefit is claimed and the chosen validation methodology - e.g. benefit of new visual encoding idiom cannot be validated by measuring the performance of the algorithm used downstream ▪ carefully select the subset of validation methods matching the levels of design where contributions are claimed
  13. Beat Signer - Department of Computer Science - bsigner@vub.ac.be 13

    March 4, 2021 Domain Validation ▪ A field study can help to validate that we are going to address real user needs ▪ observe people in real-world settings ▪ semi-structured interviews (e.g. contextual inquiry) ▪ Downstream validation can for example investigate a solution's adoption rate by the target audience ▪ see what target users do of their own accord
  14. Beat Signer - Department of Computer Science - bsigner@vub.ac.be 14

    March 4, 2021 Abstraction Validation ▪ Identified task abstraction and data abstraction might not solve the target audience's problems ▪ Downstream validation includes testing the solution with members of the target audience ▪ anecdotal (qualitative) feedback whether the tool is useful ▪ field study to observe and document how the target audience uses the tool in their real-world workflow - observe changes in behaviour rather than documenting existing work practices
  15. Beat Signer - Department of Computer Science - bsigner@vub.ac.be 15

    March 4, 2021 Idiom Validation ▪ Justify the design of the idiom with respect to known perceptual and cognitive principles ▪ Heuristic evaluation or expert reviews may be used to ensure that no known guidelines are violated ▪ Downstream validation ▪ controlled experiments in a lab setting (lab study) - controlled experiments for testing the performance of specific idioms - measure time and errors for given tasks ▪ presentation and qualitative discussion of results - show images or videos of the solution to the target audience ▪ quantitative measurement of resulting visualisations (quality metrics) such as the number of edge crossings for node-link graph ▪ usability studies
  16. Beat Signer - Department of Computer Science - bsigner@vub.ac.be 16

    March 4, 2021 Algorithm Validation ▪ Analyse computational complexity of algorithms ▪ number of items in the dataset, number of pixels, … ▪ Downstream validation ▪ execution time ▪ memory consumption ▪ scalability ▪ Correctness of algorithm ▪ does implementation meet the idiom specification ▪ Standard benchmarks might help to compare algorithms
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    March 4, 2021 MatrixExplorer
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    March 4, 2021 MatrixExplorer Validation Methods
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    March 4, 2021 Genealogical Graphs
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    March 4, 2021 Genealogical Graphs Validation Methods
  21. Beat Signer - Department of Computer Science - bsigner@vub.ac.be 21

    March 4, 2021 Flow Maps Migration from California Top ten states that sent migrants to California (green) and to New York (blue)
  22. Beat Signer - Department of Computer Science - bsigner@vub.ac.be 22

    March 4, 2021 Flow Maps Validation Methods
  23. Beat Signer - Department of Computer Science - bsigner@vub.ac.be 23

    March 4, 2021 LiveRAC
  24. Beat Signer - Department of Computer Science - bsigner@vub.ac.be 24

    March 4, 2021 LiveRAC Validation Methods
  25. Beat Signer - Department of Computer Science - bsigner@vub.ac.be 25

    March 4, 2021 LinLog Validation Methods
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    March 4, 2021 Sizing the Horizon Validation Methods
  27. Beat Signer - Department of Computer Science - bsigner@vub.ac.be 27

    March 4, 2021 Exercise 4 ▪ Analysis and Validation
  28. Beat Signer - Department of Computer Science - bsigner@vub.ac.be 28

    March 4, 2021 Further Reading ▪ This lecture is mainly based on the book Visualization Analysis & Design ▪ chapter 4 - Analysis: Four Levels for Validation
  29. Beat Signer - Department of Computer Science - bsigner@vub.ac.be 29

    March 4, 2021 References ▪ Visualization Analysis & Design, Tamara Munzner, Taylor & Francis Inc, (Har/Psc edition), May, November 2014, ISBN-13: 978-1466508910
  30. 2 December 2005 Next Lecture Data Presentation