SD&C chapter software engineeringLec 5A.ppt
- 1. Software Construction & Development User Interface Design Lecture 5A
- 2. User interface design Designing effective interfaces for software systems
- 3. Objectives To suggest some general design principles for user interface design To explain different interaction styles To introduce styles of information presentation To describe the user support which should be built-in to user interfaces To introduce usability attributes and system approaches to system evaluation
- 4. Topics covered User interface design principles User interaction Information presentation User support Interface evaluation
- 5. The user interface System users often judge a system by its interface rather than its functionality A poorly designed interface can cause a user to make catastrophic errors Poor user interface design is the reason why so many software systems are never used
- 6. Graphical user interfaces Most users of business systems interact with these systems through graphical interfaces although, in some cases, legacy text-based interfaces are still used
- 7. GUI characteristics Characteristic Description Windows Multiple windows allow different information to be displayed simultaneously on the user’s screen. Icons Icons different types of information. On some systems, icons represent files; on others, icons represent processes. Menus Commands are selected from a menu rather than typed in a command language. Pointing A pointing device such as a mouse is used for selecting choices from a menu or indicating items of interest in a window. Graphics Graphical elements can be mixed with text on the same display.
- 8. GUI advantages They are easy to learn and use. • Users without experience can learn to use the system quickly. The user may switch quickly from one task to another and can interact with several different applications. • Information remains visible in its own window when attention is switched. Fast, full-screen interaction is possible with immediate access to anywhere on the screen
- 9. User interface design process Executable prototype Design prototype Produce paper- based design prototype Produce dynamic design prototype Evaluate design with end-users Implement final user interface Evaluate design with end-users Analyse and understand user activities
- 10. UI design principles UI design must take account of the needs, experience and capabilities of the system users Designers should be aware of people’s physical and mental limitations (e.g. limited short-term memory) and should recognise that people make mistakes UI design principles underlie interface designs although not all principles are applicable to all designs
- 11. User interface design principles Principle Description User familiarity The interface should use terms and concepts which are drawn from the experience of the people who will make most use of the system. Consistency The interface should be consistent in that, wherever possible, comparable operations should be activated in the same way. Minimal surprise Users should never be surprised by the behaviour of a system. Recoverability The interface should include mechanisms to allow users to recover from errors. User guidance The interface should provide meaningful feedback when errors occur and provide context-sensitive user help facilities. User diversity The interface should provide appropriate interaction facilities for different types of system user.
- 12. Design principles User familiarity • The interface should be based on user-oriented terms and concepts rather than computer concepts. For example, an office system should use concepts such as letters, documents, folders etc. rather than directories, file identifiers, etc. Consistency • The system should display an appropriate level of consistency. Commands and menus should have the same format, command punctuation should be similar, etc. Minimal surprise • If a command operates in a known way, the user should be able to predict the operation of comparable commands
- 13. Design principles Recoverability • The system should provide some resilience to user errors and allow the user to recover from errors. This might include an undo facility, confirmation of destructive actions, 'soft' deletes, etc. User guidance • Some user guidance such as help systems, on-line manuals, etc. should be supplied User diversity • Interaction facilities for different types of user should be supported. For example, some users have seeing difficulties and so larger text should be available