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					Visualization and Interaction with Multiple Levels of Detail in Greedy Algorithms




         Visualization and Interaction
         with Multiple Levels of Detail
         in Greedy Algorithms

                              J. Ángel Velázquez-Iturbide
                             Universidad Rey Juan Carlos,
                                     Madrid, Spain
                                angel.velazquez@urjc.es



               PVW 2011, Darmstadt, June 2011
Visualization and Interaction with Multiple Levels of Detail in Greedy Algorithms




     Outline
   1.      Introduction
   2.      Design of the GreedEx system
   3.      Experience and evaluation
   4.      Conclusions and future work




               PVW 2011, Darmstadt, June 2011
Visualization and Interaction with Multiple Levels of Detail in Greedy Algorithms




     1 Introduction
   •       AV systems:
         –      Should be designed aimed at clear goals
   •       Tasks supported:
         –      As stated or deduced from the literature:
               •     Understanding behavior
               •     Some gathering of performance measures
               •     Some comparing of algorithms
               •     Some evaluation of assignments
               •     …




               PVW 2011, Darmstadt, June 2011
Visualization and Interaction with Multiple Levels of Detail in Greedy Algorithms




     1 Introduction
   •       Hypothesis:
         –      The use of explicit, clear pedagogical goals
                increases the quality and effectiveness of an AV
                system
   •       This allows:
         –      Identifying visualization and interaction
                requirements of the AV system
         –      Broadening the range of educational goals may
                result in broadening the range of features
                supported by the AV system
         –      Checking alignment of educational goals of the AV
                system with instructional activities

               PVW 2011, Darmstadt, June 2011
Visualization and Interaction with Multiple Levels of Detail in Greedy Algorithms




     1 Introduction
   •       We illustrate our claim with GreedEx:
         –      Interactive assistant to experiment with
                selection functions in greedy algorithms
         –      It supports a fixed, extensible set of problems
   •       GreedEx pedagogical goals:
         –      Comprehension level:
               •     Understand the behavior of the greedy algorithm for
                     different input data and selection functions
         –      Analysis level:
               •     Analyze the effect of selection functions
         –      Evaluation level:
               •     Evaluate the outcomes of selection functions and
                     decide which are optimal
               PVW 2011, Darmstadt, June 2011
Visualization and Interaction with Multiple Levels of Detail in Greedy Algorithms




     1 Introduction
    •       Demo




               PVW 2011, Darmstadt, June 2011
Visualization and Interaction with Multiple Levels of Detail in Greedy Algorithms


     2 Multiple levels of detail in
     greedy algorithms
   • Experimentation involves large amounts of
     data:
         – Multiple levels of detail and multiple
           representations
   • Generation of data:
         – Random generation, from a file or interactively




               PVW 2011, Darmstadt, June 2011
Visualization and Interaction with Multiple Levels of Detail in Greedy Algorithms


     2 Multiple levels of detail in
     greedy algorithms
   • Single set of input data, single
     selection function:
         – Learning goals:
               • Comprehension level:
                     – Understand the algorithm behavior with the given
                       input data and selection function
               • Analysis level:
                     – Analyze the effect of the selection function
         – Conventional animation


               PVW 2011, Darmstadt, June 2011
Visualization and Interaction with Multiple Levels of Detail in Greedy Algorithms


     2 Multiple levels of detail in
     greedy algorithms
   • Single set of input data, single
     selection function:
         – System elements:
               • Visualization panel:
                     – Visualization colors and tones
                     – Animation controls
               • Results table:
                     – Several columns about the execution sequence and
                       result




               PVW 2011, Darmstadt, June 2011
Visualization and Interaction with Multiple Levels of Detail in Greedy Algorithms


     2 Multiple levels of detail in
     greedy algorithms
   • Single set of input data, multiple
     selection functions:
         – Learning goals:
               • Analysis level:
                     – Analyze the effect of the different selection
                       functions
               • Evaluation level:
                     – Evaluate the outcomes of the different
                       selection functions and decide which are
                       optimal for this execution
         – Execute all (or a subset of) all the
           selection functions
               PVW 2011, Darmstadt, June 2011
Visualization and Interaction with Multiple Levels of Detail in Greedy Algorithms


     2 Multiple levels of detail in
     greedy algorithms
   • Single set of input data, multiple
     selection function:
         – System elements:
               • Results table:
                     – Results column




               PVW 2011, Darmstadt, June 2011
Visualization and Interaction with Multiple Levels of Detail in Greedy Algorithms


     2 Multiple levels of detail in
     greedy algorithms
   • Multiple set of input data, multiple
     selection functions:
         – Learning goals:
               • Evaluation level:
                     – Evaluate the outcomes of selection functions
                       and decide which are optimal
         – A high number of executions




               PVW 2011, Darmstadt, June 2011
Visualization and Interaction with Multiple Levels of Detail in Greedy Algorithms


     2 Multiple levels of detail in
     greedy algorithms
   • Multiple set of input data, multiple
     selection function:
         – System elements:
               • History table:
                     – Highlighting
               • Summary table




               PVW 2011, Darmstadt, June 2011
Visualization and Interaction with Multiple Levels of Detail in Greedy Algorithms


     2 Multiple levels of detail in
     greedy algorithms
   • Need to examine past results:
         – For the same data set and selection
           function:
               • Backwards animation controls
   • Connection between levels:
         – For the same data set and a different
           selection function:
               • Connection between a row in the results table and
                 an animation
         – For different data set:
               • Connection between a cell in the history table and
                 an animation
               PVW 2011, Darmstadt, June 2011
Visualization and Interaction with Multiple Levels of Detail in Greedy Algorithms




     3 Experience and evaluation
   • Development of GreedEx:
         – Initial specification based on learning goals
         – Visualizations inspired on textbooks
           figures
         – Several preliminary assistants
         – Educational facilities:
               • Export visualizations, animations and tables
               • Multilingual support
         – Evolution guided by usability evaluations
         – It currently supports 6 problems


               PVW 2011, Darmstadt, June 2011
Visualization and Interaction with Multiple Levels of Detail in Greedy Algorithms




     3 Experience and evaluation
   • Experience:
      – 4 academic years
      – The core of two lab assignments
      – Complementary research based on
        analysis of students’ reports:
               • Identification of misconceptions
               • Intervention on the teaching method




               PVW 2011, Darmstadt, June 2011
Visualization and Interaction with Multiple Levels of Detail in Greedy Algorithms




     3 Experience and evaluation
   • Usability evaluations:
     – Expert evaluations:
               • Conformance to specifications
               • Cognitive tours
               • Heuristic evaluation
         – Cuestionnaires:
               • 5 evaluations
               • The students had to perform 3 tasks:
                     – Use Greedex to determine the optimal selection
                       functions for the activity selection problem
                     – Fill and submit a short report
                     – Fill and deliver a questionnaire
               PVW 2011, Darmstadt, June 2011
Visualization and Interaction with Multiple Levels of Detail in Greedy Algorithms




     3 Experience and evaluation
   • Usability evaluations:
         – General results:




               PVW 2011, Darmstadt, June 2011
Visualization and Interaction with Multiple Levels of Detail in Greedy Algorithms




     3 Experience and evaluation
   • Usability evaluations:
         – Results of its main visual elements:




               PVW 2011, Darmstadt, June 2011
Visualization and Interaction with Multiple Levels of Detail in Greedy Algorithms




     4 Conclusions
   • GreedEx:
         – Interactive assistant to experiment with
           selection functions in greedy algorithms
         – Extensible, supporting a fixed set of problems
         – Design based on learning goals
         – Evolution based on usability evaluations
         – The most important interaction categories:
               •   Abstract/elaborate (levels of detail)
               •   Explore (animation)
               •   Rearrange (behavior of selection functions)
               •   Connect (levels of detail)

               PVW 2011, Darmstadt, June 2011
Visualization and Interaction with Multiple Levels of Detail in Greedy Algorithms




     4 Conclusions
   • Work in progress:
         – “Final” version
         – Evaluation of educational efficiency for
           greedy algorithms
   • Future work:
         – Support to collaborative discussion
         – Generalization to support a domain of
           problems:
               • Probably, loss of some attractive, problem-
                 specific elements


               PVW 2011, Darmstadt, June 2011
Visualization and Interaction with Multiple Levels of Detail in Greedy Algorithms




           Thank you very much!
                Questions?



               PVW 2011, Darmstadt, June 2011

				
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posted:9/10/2011
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