CS 501: Software EngineeringAdministrationSlide 3EvaluationSlide 5MeasurementEvaluation based on measurementsEvaluation with UsersEvaluation with Users PreparationUsability LaboratoryEvaluation with Users Sessions ConductEvaluation with users: Results analysisUsability: Design Tensions in Networked SystemsSystem considerations of user interface designUsability and CostChanges in user interface design1990PowerPoint Presentation2003Slide 20Slide 212006Slide 23Slide 24Slide 25Slide 26Slide 27System Architecture and DesignUML: System and Subsystem ModelingUML Notation: Component & NodeComponents and ReplaceabilitySystem Architecture Example: Extensibility in Web BrowsersWeb Interface: BasicUML Notation: Deployment DiagramUML Notation: Application Programming Interface (API)UML Notation: InterfacesWeb User Interface: CGI ScriptUML Notation: CGI Interface DiagramWeb User Interface: JavaScriptUML Notation: PackageExample: Web BrowserWeb User Interface: AppletApplet InterfacesUML Diagrams and SpecificationsComponents and ClassesSystem Design: Data Intensive SystemsExample: Electricity Utility Billing Transaction TypesBatch Processing Design Example: Electricity Utility BillingCriticisms of First AttemptBatch Processing: ValidationUML Deployment Diagram: Batch Processing ValidationBatch Processing: Master File UpdateInterfaces to DataInputBenefits of Batch UpdatingOnline InquiryOnline Inquiry: Use CasesData Intensive Systems Example: A Small-town StockbrokerA Database ArchitectureReal-time TransactionsReal-time Transactions & Batch ProcessingStock Broker: Interface DiagramPractical considerations to include in Architecture and Specification1CS 501 Spring 2008CS 501: Software EngineeringLecture 13System Architecture and Design I2CS 501 Spring 2008AdministrationQuizzesThere are 4 quizzes, each with 2 questions. The final grade will be based on the best 6 questions out of 8.Uncollected answer books are at 301 College Avenue.Average grades:Quiz 1 Q1 Quiz 1, Q2 Quiz 2 Q1 Quiz 2 Q2 7.6 6.2 6.8 8.03CS 501 Spring 2008CS 501: Software EngineeringUsability (continued)4CS 501 Spring 2008Evaluation• Making sure that a system is usable before launching it.• Iterative improvements after launch.• Categories of evaluation methods:Analytical evaluation: without usersMeasurements on operational systemsEmpirical evaluation: with users5CS 501 Spring 2008EvaluationHow do you measure usability?Usability comprises the following aspects:•Effectiveness – the accuracy and completeness with which users achieve certain goals Measures: quality of solution, error rates•Efficiency – the relation between the effectiveness and the resources expended in achieving themMeasures: task completion time, learning time, clicks number•Satisfaction – the users' comfort with and positive attitudes towards the use of the systemMeasures: attitude rating scalesFrom ISO 9241-116CS 501 Spring 2008MeasurementBasic concept: log events in the users' interactions with a systemExamples from a Web system• Clicks (when, where on screen, etc.)• Navigation (from page to page)• Keystrokes (e.g., input typed on keyboard)• Use of help system• ErrorsMay be used for statistical analysis or for detailed tracking of individual user.7CS 501 Spring 2008Evaluation based on measurementsAnalysis of system logs• Which user interface options were used?• When was was the help system used?• What errors occurred and how often?• Which hyperlinks were followed (click through data)?Human feedback• Complaints and praise• Bug reports• Requests made to customer service8CS 501 Spring 2008Evaluation with UsersTesting the system, not the users!Stages of evaluation with users:PreparationSessions conductAnalysis of resultsUser testing is time-consuming, expensive, and essential.9CS 501 Spring 2008Evaluation with UsersPreparation•Determine goals of the usability testing“Can a user find the required information in no more than 2 minutes?”•Write the user tasks“Answer the question: how hot is the sun?” •Recruit participantsUse the descriptions of users from the requirements phase to detect potential users10CS 501 Spring 2008Usability LaboratoryConcept: monitor users while they use systemEvaluators Userone-way mirror11CS 501 Spring 2008Evaluation with UsersSessions Conduct•Conduct the session–Usability Lab–Simulated working environment•Observe the user–Human observer(s)–Video camera–Audio recording•Inquire satisfaction data12CS 501 Spring 2008Evaluation with users:Results analysis•If possible, use statistical summaries.•Pay close attention to areas where users–were frustrated–took a long time–could not complete tasks •Respect the data and users' responses. Do not make excuses for designs that failed. •Note designs that worked and make sure they are incorporated in the final product.13CS 501 Spring 2008Usability: Design Tensions in Networked Systems• Client computers and network connections vary greatly in capacity• Client software may run on various operating systems. It may be current or an earlier version. What assumptions do you make about the user's computer and Web browser?• Designers wish to control client software, e.g., Web browsers, but users wish to configure their own environments. This can be a factor in accessibility, e.g., which part of the system determines the font size.14CS 501 Spring 2008System considerations of user interface design• Personal computer cycles are there to be used• Any network transfer involves delay• Shared systems have unpredictable performance• Data validation often requires access to shared data• Mobile code poses security risks15CS 501 Spring 2008Usability and Cost• Good usability may be expensive in hardware or special software development• User interface development may be a major part of a software development projectProgramming environments provide powerful user interface toolkits• Costs are multiplied if a user interface has to be used on different computers or migrate to different versions of systemsWeb browsers provide a general purpose user interface where others maintain the user interface software16CS 501 Spring 2008Changes in user interface designExamples of change: 1995 to 200717CS 501 Spring 20081990SEARCH I NSPEC Dat abase- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -Type keywor ds and pr
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