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HCI'2000 Tutorial - Model-based Design and Evaluation of Interactive Applications

Model-Based Design and Evaluation of Interactive Applications

Fabio Paternò

CNUCE-C.N.RPisa, Italy


n Introduction to Model-based Approaches n State of art in Task Modelsn ConcurTaskTreesn Task Models for Cooperative Applicationsn Exercisen Task Models in User Interface Designn Task Models in Usability Evaluation

Structure of the Tutorial


Why Model-based approaches?

Highlight important informationHelp to manage complexity Useful to support methods


Significant Models in HCI

Task modelsCognitive architecturesUser modelsDomain ModelsContext ModelsPresentation ModelsDialogue models


UML and HCI

Model-based approachNine notationsLack of consideration of the user interface How to improve it?


TaskGoalBasic TaskTask AnalysisTask Model

Definitions


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

Task Analysis (example)


Engineering task models

Flexible and expressive notations with a precise semanticsSystematic methods able to indicate how to use information in the task modelsAvailability of automatic tools to use such information efficiently


The many possible task models

Existing System Envisioned System User


Use of Task Models

Improve understanding of the application domainRecord the result of interdisciplinary discussionSupport effective designSupport usability evaluationSupport the user during a sessionDocumentation


Representations of Task Models

Hierarchical task analysisGOMS familyUANDifferent syntax (textual vs graphical)Different level of formalityDifferent set of operators for task composition


GOMS Example

GOAL: EDIT-MANUSCRIPTGOAL: EDIT-UNIT-Task repeat until no more unit tasks

GOAL: ACQUIRE-UNIT-TASKGET-NEXT-PAGE if at end of manuscriptGET-NEXT-TASK

GOAL: EXECUTE-UNIT-TASKGOAL:LOCATE-LINE

[select: USE-QS-METHODUSE-LF-METHOD]

GOAL: MODIFY-TEXT[select: USE-S-METHOD

USE-M-METHOD]VERIFY-EDIT


Limitations of GOMS

It does not consider user errorsIt does not consider the possibility of interruptionsIt considers only sequential tasksIt can be inadequate for distributed applications (such as web-based applications)


UAN - User Action Notation

The user interface is represented by a hierarchy of asynchronous tasksuser action and system feedback are specified at a low leveltextual notation


Example of UAN specification

Task: BuildRequest:((SelR | ClearR | IconifyR)*--> SpecField+)

Task: SelApplicationUser Action Interface Feedback Interface State~[x,y in AppICON]∨∧(t<tdoubleClick) ∨∧ w’!: w’-!

UnMap(PrevAppliMenu)Map(AppMenu)UnMap(AppICON)

CurAppli=AppCurMenu=AppMenu


ConcurTaskTrees

Focus on Activities Hierarchical StructureGraphical SyntaxRich set of temporal operatorsTask allocationObjects and task attributes


Task Models vs Scenarios

Scenarios are informal descriptions of a specific use in a specific contextTask models describe the possible activities and their relationshipsScenarios can support task developmentTask models can support scenarios identification


Moving from scenarios to tasks


Temporal operators

Enabling T1 >> T2 or T1 [ ]>> T2

Disabling T1 [> T2

Interruption T1 |> T2

Choice T1 [ ] T2

Iteration T1* or T1{n}

Concurrency T1 ||| T2 T1 |[]| T2

Optionality [T]


Task Types

Interaction tasksSelection

Edit

Control

…

Application taskOverview

Comparison

Locate

Grouping

...


Inheritance of relationships


Relationships task/subtasks


Optional tasks


Tool Support in CTTE

Flexible editing of the task modelUsing informal descriptions in modelling Checking completeness of the specificationSaving the specification in various formatsSimulating the task model Comparing task modelsRunning scenarioshttp://giove.cnuce.cnr.it/ctte.html


The CTTE editor


Simulating dynamic behaviour


Comparison of Task Models


Modelling Multi-UserApplications

User1

User2 User3

Cooperative part

t1t2

t3

t1(User1) t3 (User3)


Cooperative aspects


Exercise

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


Limitations of current approaches in UI design

Visual tools do not support mapping between logical activities and UI elementsUML is oriented to the system designNo available tools for task-based design (when existing, not publicly available and limited functionality)


Task model - based design

1. Analysis of operators amongst tasks

Identify structure of dialogues

2. Analysis of each task (objects, attributes, ...)

Choose a suitable presentation


Task-based design

Temporal relationships among tasksFrequency of single task and task patternsInteraction and presentations techniques suitable for task types considering type and cardinality of dataMultiple consistent representations when an object supports multiple tasksAutomatic support to cognitive intense problem solving user tasks


Criteria to identify presentations

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


Mapping task-interaction technique: single choice exam.

Knowndomain:

Number of pos-sible values∈[2,3]Number of pos-sible values∈[4,7]

Number of pos-sible values∈ [8,50]

Number of pos-sible values∈ ]50,+∞[


Disabling tasks ([>) should be located so as to highlight their control function

Control tasks


Grouping tasks that share the same parent taskCommunicating concurrent tasks (|[]|) are presented close to each other

The task model structure


Both sets are shown in the same presentation unit (when they exchange information, []>>)The sets are presented at different timesThe sets are presented in different presentation unit at the same time

Supporting enabling operator

Jo*

SubmitName:

Name AgeJohansen 52Jones 27Joxibon 18

Jo*

Submit

Name:Age:

Name AgeJohansen 52Jones 21

Results:

>20Results:

Situation 1 Situations 2 and 3


Deriving information from operators


Task-interface relationships


Tasks-interface relationships


Tasks-interface relationships


The Aerodrome case study


An excerpt of task model


The resulting dialogues -1






Mobi-D: Example of tool-support for model-based design


Task Patterns

Identification of solutions for problems recurring in different applicationsReuse of both design and software solutionsPossibility of obtaining more compact specifications


Patterns

P1 NameP2 ProblemP3 Task specificationP4 Objects specificationP5 Scenario of useP6 Possible subpattersP7 Aspects which can varyP8 Applications that can use it


Adaptation

Adaptibility vs AdaptivityDimensions: User, Device, Context, ...Usability issues


Different initial accesses

TouristStudent Expert


Different presentations


What is it?

Techniques supported (direct guidance, adaptive ordering, hiding, annotation)

AdvantagesDisadvantages

What about adaptive support?


Example of adaptive support


Exercise

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


Usability Evaluation

Heuristic evaluationCognitive Walkthrough GuidelinesEmpirical testingModel-based evaluation


Inspection-based Evaluation

Use of CTT models in the evaluation phaseUse of a the set of deviation typesTo evaluate a prototype


The method

Development of task model of the application to evaluateAnalysis of deviations related to basic tasksAnalysis of deviations in high-level tasksInterdisciplinary analysis


Organisation of the exercise

Introduction of the methodIntroduction of the prototypeShort use of the prototypePrototype available during exerciseTask model available to evaluatorsAudio record


Organisation of the exercise

Evaluators drive discussionQuestions derived from task model + classes of deviationsThey are related to user interface elementsIdentification of the information necessary for each task performanceTables (useful more as documentation or design rationale)


Refined guidewords(basic tasks)

NONE: initial information, performance, resultOTHER THAN: less, more, differentILL-TIMED: too early, too late


Resulting tablesTask: Check Deviation Guideword: NoneExplanation Causes Consequences Protections Recommendations

The system isbroken.Perceptionproblem

The controllerhas not anupdated view ofthe air traffic

The controllerlooks at thewindow tocheck the airtraffic

Duplication ofcommunication system

No inputThe controllerhas notinformationconcerning thecurrent traffic

Controller isdistracted orinterrupted byother activitiesPerceptionproblem

Pilot callscontroller tocheck the path

NoperformanceThe controllerhas theinformationbut he doesn’tcheck itcarefully

Controller isdistracted or overconfidentInterpretationproblem

No outputThe controllerfinds adeviation butimmediatelyforgets it

Controller isinterrupted byother activities

Pilot callscontroller tocheck the path

Provide an automaticwarning message onlywhen an aircraft isdeviating from theassigned path.


Interpretation for high-level tasks

NONE: initial information, performance, resultOTHER THAN: less, more, differentILL-TIMED: too early, too late


The MIDAS User Interface


Example of issue (1)

Check deviation - NONE/No performanceCauses: workload, memoryProtection: Red line connecting two flight labelsRecommendation: possibility of audio warning



Check deviation - NONE/No inputCauses: Zoom activatedProtection: Button to default viewRecommendation: Two views (global+local)



Send stop … - Different performanceCauses: action slipProtection: send immediately new clearanceRecommendation: Highlight the most safety-critical element


Social constraints

Developers tend to defend every decision takenUsers tend to divagate (sometimes useful, sometimes confusing)Time pressure


RemUSINERemote USability INterface Evaluator

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


The architecture of RemUSINE

Logging tool

ConcurTaskTreesEditor

Designer

User1 logs

Task model

Log-task table Evaluation Method(RemUSINE)

Designer

Application

User1

….……. Application

Usern

RemUSINE(Preparation)

Logging tool

Usern logs….

…….

Designer site

User1 site Usern site


The Preparation Part


An example of analysis

1.JS.applet("Insertions",0).member(“..”).multiClick(124,93,16,1);2. JS.delay(7310);3.JS.applet("Insertions",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”).buttonPress();7.JS.applet(...).member(“…”).member(“…”).select(4,"XX sec.");


General Information


Automatic analisys of the log


Task Patterns


Analysis of time performance


Errors Detected (example 1)


How to interpret the results

Task model mismatchThe application is too rigidThe user interface does not provide enough support to understand how to perform the tasksRemUSINE points out where the problem is!


Results of RemUSINE

The analysis is reliable and completeIdentifying the violated precondition helps to understand the reason for the errorIt gives indication of tasks never performedIt provides quantitative information


Time required by RemUSINE

Developing the task model Record of logs using a logging toolPreparation part of RemUSINEGeneration of the resultsAnalysis of the results provided by

RemUSINE


Summary on RemUSINE

Suitable for graphical applications with a well defined set of tasks to supportUseful especially for medium-large applications with dynamic dialogues and many remote usersIt can be complemented with interviews on the parts found problematicAutomatic generation of multimedia reports on the usability problems detected


Research agenda

Models for context of useUse of task model to design adaptive interfaces supporting variety of devicesPatterns in HCIComputer-aided analysis of task modelsIntegrating task models in UML to better support design of interactive applications


Conclusions and acknowledgements

Http://giove.cnuce.cnr.it/ctte.htmlhttp://giove.cnuce.cnr.it/remusine.htmlGUITARE Project http://giove.cnuce.cnr.it/guitare.htmlMEFISTO Project http://giove.cnuce.cnr.it/mefisto.htmlBook on Model-Based Design and Evaluation of Interactive Applications, Springer [email protected]

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