1 User Interface Design User Interface Design Designing effective Designing effective interfaces interfaces for software systems for software systems Importance of user interface Importance of user interface 2 • System users often judge a system • System users often judge a system by its interface rather than its by its interface rather than its functionality functionality • A poorly designed interface can cause A poorly designed interface can cause • a user to make catastrophic errors a user to make catastrophic errors • Poor user interface design is the Poor user interface design is the • reason why so many software systems reason why so many software systems are never used are never used 1
Graphical user interfaces Graphical user interfaces 3 • Most users of business systems Most users of business systems • interact with these systems through interact with these systems through graphical user interfaces (GUIs) graphical user interfaces (GUIs) – although, in some cases, legacy text although, in some cases, legacy text- - – based interfaces are still used based interfaces are still used GUI characteristics GUI characteristics 4 • • Windows Windows • • Icons Icons • • Menus Menus • • Pointing Devices Pointing Devices • Graphics • Graphics 2
GUI advantages GUI advantages 5 • • They are easy to learn and use They are easy to learn and use – – Users without experience can learn to Users without experience can learn to use the system quickly use the system quickly • The user may switch quickly from one The user may switch quickly from one • task to another and can interact with task to another and can interact with several different applications several different applications – – Information remains visible in its own Information remains visible in its own window when attention is switched window when attention is switched • • Fast, full Fast, full- -screen interaction is screen interaction is possible with immediate access to possible with immediate access to anywhere on the screen anywhere on the screen User- -centred design centred design User 6 • User • User- -centred design is an approach to centred design is an approach to UI design where the needs of the UI design where the needs of the user are paramount and where the user are paramount and where the user is involved in the design process user is involved in the design process • UI design UI design always always involves the involves the • development of prototype interfaces development of prototype interfaces 3
User interface design process User interface design process 7 Analyze and Produce Analyze and Produce Evaluate design Evaluate design understand paper-based understand paper-based With end-users With end-users user activities design prototype user activities design prototype Design Produce dynamic Evaluate design Design Produce dynamic Evaluate design prototype Design prototype With end-users prototype Design prototype With end-users Executable Implement final Executable Implement final prototype user interface prototype user interface UI design principles UI design principles 8 • UI design must take account of the UI design must take account of the • needs, experience and capabilities of needs, experience and capabilities of the system users the system users • Designers should be aware of people’s • Designers should be aware of people’s physical and mental limitations (e.g. physical and mental limitations (e.g. limited short- -term memory) and term memory) and limited short should recognize that people make should recognize that people make mistakes mistakes • • UI design principles underlie UI design principles underlie interface designs although not all interface designs although not all principles are applicable to all designs principles are applicable to all designs 4
User interface design principles User interface design principles 9 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. Design principles Design principles 10 • User familiarity • User familiarity – The interface should be based on user The interface should be based on user- -oriented oriented – terms and concepts rather than computer terms and concepts rather than computer concepts. concepts. • • For example, an office system should use concepts For example, an office system should use concepts such as letters, documents, folders etc., rather than such as letters, documents, folders etc., rather than directories, file identifiers, etc. directories, file identifiers, etc. • Consistency • Consistency – The system should display an appropriate level The system should display an appropriate level – of consistency. Commands and menus should of consistency. Commands and menus should have the same format, command punctuation have the same format, command punctuation should be similar, etc. should be similar, etc. • • Minimal surprise Minimal surprise – If a command operates in a known way, the user If a command operates in a known way, the user – should be able to predict the operation of should be able to predict the operation of comparable commands comparable commands 5
Design principles Design principles 11 • Recoverability Recoverability • – – The system should provide some resilience to The system should provide some resilience to user errors and allow the user to recover from user errors and allow the user to recover from errors. This might include an errors. This might include an UNDO UNDO facility, facility, confirmation of destructive actions, 'soft' confirmation of destructive actions, 'soft' deletes, etc. deletes, etc. • User guidance User guidance • – – Some user guidance such as help systems, on Some user guidance such as help systems, on- - line manuals, etc. should be supplied line manuals, etc. should be supplied • User diversity User diversity • – Interaction facilities for different types of – Interaction facilities for different types of user should be supported. For example, some user should be supported. For example, some users have users have seeing seeing difficulties and so larger text difficulties and so larger text should be available should be available User- -system interaction system interaction User 12 • • Two problems must be addressed in Two problems must be addressed in interactive systems design interactive systems design – – How should information from the user be How should information from the user be provided to the computer system? provided to the computer system? – How should information from the – How should information from the computer system be presented to the computer system be presented to the user? user? • • User interaction and information User interaction and information presentation may be integrated presentation may be integrated through a coherent framework through a coherent framework 6
Interaction styles Interaction styles 13 • Direct manipulation Direct manipulation • • Menu Menu- -based (Menu selection) based (Menu selection) • • Form fill Form fill- -in in • • Command language Command language • • Natural language Natural language • Advantages and disadvantages Advantages and disadvantages Interaction Main Main Application style advantages disadvantages examples • Fast and intuitive • May be hard to • Video games Direct interaction implement • CAD systems manipulation • Easy to learn • Only suitable where there is a visual metaphor for tasks and objects • Avoids user error • Slow for experienced • Most general-purpose Menu • Little typing users systems selection required • Can become complex if many menu options Form fill-in • Simple data entry • Takes up a lot of screen • Stock control, • Easy to learn space Personal loan processing • Powerful and • Hard to learn • Operating systems, Command flexible • Poor error management Library information language retrieval systems Natural • Accessible to casual • Requires more typing • Timetable systems users • Natural language • WWW information language • Easily extended understanding systems retrieval systems are unreliable 7
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