CS 501: Software EngineeringPresentationsDesign for UsabilitySystem Considerations of User InterfacesInformation PresentationInformation Presentation: Separation of Presentation from ContentSpecial Considerations: DisabilitiesSpecial Considerations: Computer Systems and NetworksSpecial Considerations: Design Tensions in Networked SystemsSpecial Considerations: Device-Aware User InterfacesSpecial Considerations: Usability and CostThe Importance of User Interface Design1CS 501 Spring 2005CS 501: Software EngineeringLecture 12Usability 22CS 501 Spring 2005PresentationsSchedule your presentation now!!!!Available time slots are on the Notices page. Be sure to contact Anat Nidar-Levi to schedule your presentation.Your client must attend the presentation unless you have special permission.3CS 501 Spring 2005Design for UsabilityUsability of a computer system is a combination of factors:• User interface design• Functionality (functional requirements)• Performance (non-functional requirements)• Help systems and documentation• Freedom from errors4CS 501 Spring 2005System Considerations of User Interfaces• 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 risks5CS 501 Spring 2005Information PresentationSimple is often better than fancy• Text precise, unambiguousfast to compute and transmit• Graphical interfacesimple to comprehend / learnuses of colorshows variations6CS 501 Spring 2005Information Presentation: Separation of Presentation from ContentInformation to be displayedPresentation softwareDisplayPresentation softwareDisplayPDFAcrobathtmlSafari7CS 501 Spring 2005Special Considerations: Disabilities• What if the user:is visually impaired or color blind?does not speak English?is a poor typist? • There is a tradition of blind programmers• Navigation of web sites need not be only visualYou may have a legal requirement to support people with disabilities8CS 501 Spring 2005Special Considerations: Computer Systems and NetworksThe performance, reliability and predictability of computer systems and networks is crucial to usability• Response timeinstantaneous for mouse tracking and echo of key stroke5 seconds for simple transactions• Example: Pipelined algorithm for the Mercury page turner• Quality of Service for real time information9CS 501 Spring 2005Special Considerations: 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• System designers wish to control clients; users wish to configure their own environments10CS 501 Spring 2005Special Considerations: Device-Aware User Interfaces• Examples of devices:desk-top computer, fast network connectionlaptop computer, intermittent connectivityPalmPilot, synchronizationsmart telephonedigital camera, camcorder• Device-aware user interfaces are aware of:=> performance of device=> limited form factor (display, keyboard)=> connectivity11CS 501 Spring 2005Special Considerations: Usability 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 software12CS 501 Spring 2005The Importance of User Interface DesignGood support for users is more than a cosmetic flourish • Elegant design, appropriate functionality, & responsive system: => a measurable difference to their effectiveness • A system that is hard to use: => users may fail to find important results, or mis-interpret what they do find=> user may give up in disgust A computer system is only as good as the interface it provides to its
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