ModelBased Design and Evaluation of Interactive Applications

1
Model-Based Design and Evaluation of Interactive
Applications

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• Fabio Paternò
• CNUCE-C.N.R
• Pisa, Italy

2
Structure of the Tutorial

• Introduction to Model-based Approaches
• State of art in Task Models
• ConcurTaskTrees
• Task Models for Cooperative Applications
• Exercise
• Task Models in User Interface Design
• Task Models in Usability Evaluation

3
Why Model-based approaches?

• Highlight important information
• Help to manage complexity
• Useful to support methods

4
Significant Models in HCI

• Task models
• Cognitive architectures
• User models
• Domain Models
• Context Models
• Presentation Models
• Dialogue models

5
UML and HCI

• Model-based approach
• Nine notations
• Lack of consideration of the user interface
• How to improve it?

6
Definitions

• Task
• Goal
• Basic Task
• Task Analysis
• Task Model

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Task Analysis (example)

• Tourist
• general and clear information in limited
  amount
• access by spatial representations
• guided navigation
• Art student
• some basic knowledge
• choice among different types of information
  
• Expert
• precise requests
• detailed description of the information
  requested

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Engineering task models

• Flexible and expressive notations with a precise
  semantics
• Systematic methods able to indicate how to use
  information in the task models
• Availability of automatic tools to use such
  information efficiently

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The many possible task models

• Existing System
• Envisioned System
• User

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Use of Task Models

• Improve understanding of the application domain
• Record the result of interdisciplinary discussion
• Support effective design
• Support usability evaluation
• Support the user during a session
• Documentation

11
Representations of Task Models

• Hierarchical task analysis
• GOMS family
• UAN
• Different syntax (textual vs graphical)
• Different level of formality
• Different set of operators for task composition

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GOMS Example
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Limitations of GOMS

• It does not consider user errors
• It does not consider the possibility of
  interruptions
• It considers only sequential tasks
• It can be inadequate for distributed applications
  (such as web-based applications)

14
UAN - User Action Notation

• The user interface is represented by a hierarchy
  of asynchronous tasks
• user action and system feedback are specified at
  a low level
• textual notation

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Example of UAN specification
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ConcurTaskTrees

• Focus on Activities
• Hierarchical Structure
• Graphical Syntax
• Rich set of temporal operators
• Task allocation
• Objects and task attributes

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Task Models vs Scenarios

• Scenarios are informal descriptions of a specific
  use in a specific context
• Task models describe the possible activities and
  their relationships
• Scenarios can support task development
• Task models can support scenarios identification

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Moving from scenarios to tasks
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Temporal operators
Enabling T1 gtgt T2 or T1 gtgt T2 Disabling
T1 gt T2 Interruption T1 gt T2 Choice T1
T2 Iteration T1 or T1n Concurrency T1
T2 T1 T2 Optionality T
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Task Types
Interaction tasks Selection Edit Control Applica
tion task Overview Comparison Locate Grouping ...
21
Inheritance of relationships
22
Relationships task/subtasks
23
Optional tasks
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Tool Support in CTTE

• Flexible editing of the task model
• Using informal descriptions in modelling
• Checking completeness of the specification
• Saving the specification in various formats
• Simulating the task model
• Comparing task models
• Running scenarios
• http//giove.cnuce.cnr.it/ctte.html

25
The CTTE editor
26
Simulating dynamic behaviour
27
Comparison of Task Models
28
Modelling Multi-User Applications
29
Cooperative aspects
30
Exercise

• Develop a task model in ConcurTaskTrees with at
  least three levels and ten tasks using the CTTE
  tool

31
Limitations of current approaches in UI design

• Visual tools do not support mapping between
  logical activities and UI elements
• UML is oriented to the system design
• No available tools for task-based design (when
  existing, not publicly available and limited
  functionality)

32
Task model - based design
1. Analysis of operators amongst tasks
2. Analysis of each task (objects, attributes,
...)
Identify structure of dialogues
Choose a suitable presentation
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Task-based design

• Temporal relationships among tasks
• Frequency of single task and task patterns
• Interaction and presentations techniques suitable
  for task types considering type and cardinality
  of data
• Multiple consistent representations when an
  object supports multiple tasks
• Automatic support to cognitive intense problem
  solving user tasks

34
Criteria to identify presentations

• One single presentation supporting all possible
  tasks
• As many presentations as the number of enabled
  task sets
• Intermediate solution

35
Mapping task-interaction technique single choice
exam.
Known domain
36
Control tasks

• Disabling tasks (gt) should be located so as to
  highlight their control function

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The task model structure

• Grouping tasks that share the same parent task
• Communicating concurrent tasks () are
  presented close to each other

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Supporting enabling operator

• Both sets are shown in the same presentation unit
  (when they exchange information, gtgt)
• The sets are presented at different times
• The sets are presented in different presentation
  unit at the same time

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Deriving information from operators
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Task-interface relationships
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Tasks-interface relationships
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Tasks-interface relationships
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The Aerodrome case study
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An excerpt of task model
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The resulting dialogues -1
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The resulting dialogues -2
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The resulting dialogues -3
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Mobi-D Example of tool-support for model-based
design
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Task Patterns

• Identification of solutions for problems
  recurring in different applications
• Reuse of both design and software solutions
• Possibility of obtaining more compact
  specifications

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Patterns

• P1 Name
• P2 Problem
• P3 Task specification
• P4 Objects specification
• P5 Scenario of use
• P6 Possible subpatters
• P7 Aspects which can vary
• P8 Applications that can use it

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Adaptation

• Adaptibility vs Adaptivity
• Dimensions User, Device, Context, ...
• Usability issues

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Different initial accesses

Tourist
Student
Expert
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Different presentations
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What about adaptive support?

• What is it?
• Techniques supported (direct guidance, adaptive
  ordering, hiding, annotation)
• Advantages
• Disadvantages

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Example of adaptive support
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Exercise

• Design a user interface corresponding to the task
  model developed in the previous exercise

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Usability Evaluation

• Heuristic evaluation
• Cognitive Walkthrough
• Guidelines
• Empirical testing
• Model-based evaluation

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Inspection-based Evaluation

• Use of CTT models in the evaluation phase
• Use of a the set of deviation types
• To evaluate a prototype

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The method

• Development of task model of the application to
  evaluate
• Analysis of deviations related to basic tasks
• Analysis of deviations in high-level tasks
• Interdisciplinary analysis

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Organisation of the exercise

• Introduction of the method
• Introduction of the prototype
• Short use of the prototype
• Prototype available during exercise
• Task model available to evaluators
• Audio record

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Organisation of the exercise

• Evaluators drive discussion
• Questions derived from task model classes of
  deviations
• They are related to user interface elements
• Identification of the information necessary for
  each task performance
• Tables (useful more as documentation or design
  rationale)

62
Refined guidewords (basic tasks)

• NONE initial information, performance, result
• OTHER THAN less, more, different
• ILL-TIMED too early, too late

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Resulting tables
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Interpretation for high-level tasks

• NONE initial information, performance, result
• OTHER THAN less, more, different
• ILL-TIMED too early, too late

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The MIDAS User Interface
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Example of issue (1)

• Check deviation - NONE/No performance
• Causes workload, memory
• Protection Red line connecting two flight labels
• Recommendation possibility of audio warning

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Example of issue (2)

• Check deviation - NONE/No input
• Causes Zoom activated
• Protection Button to default view
• Recommendation Two views (globallocal)

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Example of issue (3)

• Send stop - Different performance
• Causes action slip
• Protection send immediately new clearance
• Recommendation Highlight the most
  safety-critical element

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Social constraints

• Developers tend to defend every decision taken
• Users tend to divagate (sometimes useful,
  sometimes confusing)
• Time pressure

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RemUSINERemote USability INterface Evaluator

• Bridge between empirical and model-based
  evaluation
• Flexible and expressive task models
• Limitations of usability laboratories and need to
  decrease the costs of usability evaluation
• Application to case studies

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The architecture of RemUSINE
Designer site
Designer
ConcurTaskTrees
Task model
Editor
RemUSINE
Designer
Evaluation Method
Log-task table
(RemUSINE)
(Preparation)
User1 site
Usern site
User1 logs
Usern logs
.
Logging tool
Logging tool
.
Application
..
Application
User1
Usern
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The Preparation Part
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An example of analysis
1.JS.applet("Insertions",0).member(..).multiClic
k(124,93,16,1) 2. JS.delay(7310) 3.JS.applet("In
sertions",0).button("Sculptors").typeString("Bodin
") 4.JS.applet("Insertions",0).member("java.",0)
.multiClick(...) 5.JS.applet(...).member(,
0).typeString("Bodini Floriano", ..) 6.
JS.applet("Insertions",0).button(Periods).button
Press() 7.JS.applet(...).member().member().
select(4,"XX sec.")
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General Information
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Automatic analisys of the log
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Task Patterns
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Analysis of time performance
78
Errors Detected (example 1)
79
Errors Detected (example 2)
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Errors Detected (example 3)
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How to interpret the results

• Task model mismatch
• The application is too rigid
• The user interface does not provide enough
  support to understand how to perform the tasks
• RemUSINE points out where the problem is!

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Results of RemUSINE

• The analysis is reliable and complete
• Identifying the violated precondition helps to
  understand the reason for the error
• It gives indication of tasks never performed
• It provides quantitative information

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Time required by RemUSINE

• Developing the task model
• Record of logs using a logging tool
• Preparation part of RemUSINE
• Generation of the results
• Analysis of the results provided by RemUSINE

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Summary on RemUSINE

• Suitable for graphical applications with a well
  defined set of tasks to support
• Useful especially for medium-large applications
  with dynamic dialogues and many remote users
• It can be complemented with interviews on the
  parts found problematic
• Automatic generation of multimedia reports on the
  usability problems detected

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Research agenda

• Models for context of use
• Use of task model to design adaptive interfaces
  supporting variety of devices
• Patterns in HCI
• Computer-aided analysis of task models
• Integrating task models in UML to better support
  design of interactive applications

86
Conclusions and acknowledgements

• Http//giove.cnuce.cnr.it/ctte.html
• http//giove.cnuce.cnr.it/remusine.html
• GUITARE Project http//giove.cnuce.cnr.it/guitare.
  html
• MEFISTO Project http//giove.cnuce.cnr.it/mefisto.
  html
• Book on Model-Based Design and Evaluation of
  Interactive Applications, Springer Verlag
• fabio.paterno_at_cnuce.cnr.it