Slide 17.1 User Centred DesignThe importance of focusing on users7.2 Characteristics of Users7.4 Basics of User Interface DesignUsability vs. UtilityAspects of usabilityDifferent learning curvesSome basic terminology of user interface design7.5 Usability PrinciplesUsability PrinciplesUsability PrinciplesSlide 13Slide 14Slide 15Some encoding techniquesExample (bad UI)Example (better UI)7.6 Evaluating User InterfacesEvaluating User Interfaces7.7 Implementing a Simple GUI in JavaExampleSlide 23Slide 247.8 Difficulties and Risks in Use Case Modelling and UI DesignDifficulties and Risks in Use Case Modelling and UI DesignObject-Oriented Software EngineeringPractical Software Development using UML and JavaChapter 7: Emphasis on the User Interface Design(Taken from author’s web site and modified for classroom use by your instructor.)© Lethbridge/Laganière 2001Chapter 7: Focusing on Users and Their Tasks 27.1 User Centred Design Software development should focus on the needs of users •Understand your users •Design software based on an understanding of the users’ tasks •Ensure users are involved in decision making processes •Design the user interface following guidelines for good usability •Have users work with and give their feedback about prototypes, on-line help and draft user manuals© Lethbridge/Laganière 2001Chapter 7: Focusing on Users and Their Tasks 3The importance of focusing on users •Reduced training and support costs •Reduced time to learn the system •Greater efficiency of use •Reduced costs by only developing features that are needed •Reduced costs associated with changing the system later •Better prioritizing of work for iterative development •Greater attractiveness of the system, so users will be more willing to buy and use it© Lethbridge/Laganière 2001Chapter 7: Focusing on Users and Their Tasks 47.2 Characteristics of Users Software engineers must develop an understanding of the users•Goals for using the system •Potential patterns of use •Demographics •Knowledge of the domain and of computers •Physical ability •Psychological traits and emotional feelings© Lethbridge/Laganière 2001Chapter 7: Focusing on Users and Their Tasks 57.4 Basics of User Interface Design •User interface design should be done in conjunction with other software engineering activities. •Do use case analysis to help define the tasks that the UI must help the user perform. •Do iterative UI prototyping to address the use cases. •Results of prototyping will enable you to finalize the requirements.•“Nothing better than running the prototype by the end-users to elicit comments!”© Lethbridge/Laganière 2001Chapter 7: Focusing on Users and Their Tasks 6Usability vs. Utility Does the system provide the raw capabilities to allow the user to achieve their goal? •This is utility.Does the system allow the user to learn and to use the raw capabilities easily? •This is usability.Both utility and usability are essential •They must be measured in the context of particular types of users.© Lethbridge/Laganière 2001Chapter 7: Focusing on Users and Their Tasks 7Aspects of usability Usability can be divided into separate aspects: •Learnability—The speed with which a new user can become proficient with the system.•Efficiency of use—How fast an expert user can do their work.•Error handling—The extent to which it prevents the user from making errors, detects errors, and helps to correct errors. •Acceptability. —The extent to which users like the system.© Lethbridge/Laganière 2001Chapter 7: Focusing on Users and Their Tasks 8Different learning curves0204060801001 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31Days of learningComplexsystem,hard tolearnSimplesystem,easy tolearnSimplesystem,hard tolearn© Lethbridge/Laganière 2001Chapter 7: Focusing on Users and Their Tasks 9Some basic terminology of user interface design •Dialog: A specific window with which a user can interact, but which is not the main UI window.•Control or Widget: Specific components of a user interface.•Affordance: The set of operations that the user can do at any given point in time.•State: At any stage in the dialog, the system is displaying certain information in certain widgets, and has a certain affordance.•Mode: A situation in which the UI restricts what the user can do.•Modal dialog: A dialog in which the system is in a very restrictive mode.•Feedback: The response from the system whenever the user does something, is called feedback. •Encoding techniques. Ways of encoding information so as to communicate it to the user.© Lethbridge/Laganière 2001Chapter 7: Focusing on Users and Their Tasks 107.5 Usability Principles 1. Do not rely only on usability guidelines – always test with users.•Usability guidelines have exceptions; you can only be confident that a UI is good if you test it successfully with users.2: Base UI designs on users’ tasks.•Perform use case analysis to structure the UI.3: Ensure that the sequences of actions to achieve a task are as simple as possible.•Reduce the amount of reading and manipulation the user has to do.•Ensure the user does not have to navigate anywhere to do subsequent steps of a task.© Lethbridge/Laganière 2001Chapter 7: Focusing on Users and Their Tasks 11Usability Principles4: Ensure that the user always knows what he or she can and should do next.•Ensure that the user can see what commands are available and are not available.•Make the most important commands stand out.5: Provide good feedback including effective error messages.•Inform users of the progress of operations and of their location as they navigate.•When something goes wrong explain the situation in adequate detail and help the user to resolve the problem.© Lethbridge/Laganière 2001Chapter 7: Focusing on Users and Their Tasks 12Usability Principles 6: Ensure that the user can always get out, go back or undo an action.•Ensure that all operations can be undone.•Ensure it is easy to navigate back to where the user came from.7: Ensure that response time is adequate.•Users are very sensitive to slow response time—They compare your system to others.•Keep response time less than a second for most operations.•Warn users of longer delays and inform them of progress.© Lethbridge/Laganière 2001Chapter 7: Focusing on Users and Their Tasks