CS 501: Software EngineeringAdministrationQuiz 2, Question 1(b)Non-Functional Requirements (From Lecture 8)Quiz 2, Question 1(b) continuedRequired ReadingWhat is Design?Progress?1990PowerPoint Presentation2003Slide 12Slide 13Slide 14Slide 15Slide 16Slide 17The Design/Evaluate LoopDesign for UsabilityElements of an InterfaceLevels of UsabilityThe Conceptual ModelInterface DesignPrinciples of Interface DesignDisabilitiesFunctional DesignSame Functions, Different InterfaceData and MetadataComputer Systems and NetworksDesign Tensions in Networked SystemsUser Interfaces: Iterative Design1CS 501 Spring 2003CS 501: Software EngineeringLecture 13Usability 12CS 501 Spring 2003Administration3CS 501 Spring 2003Quiz 2, Question 1(b)A bank has many small branches. The bank is developing a new computer system to be used at all its branches. It will be used by the staff who serve customers directly, by the office staff at each branch, and by the staff at the head office.You are a member of a team that is developing the requirements for this system.(b) List four possible non-functional requirements that might be important for this application. (Be specific. General answers, such as, "the system must be reliable", are not adequate.)4CS 501 Spring 2003Non-Functional Requirements (From Lecture 8)Product requirementsperformance, reliability, portability, etc...Organizational requirementsdelivery, training, standards, etc...External requirementslegal, interoperability, etc...Requirements about the context in which the system is built:documentation and training, resources, security, physical environment, quality assurance5CS 501 Spring 2003Quiz 2, Question 1(b) continued1. When head office computers are unavailable, counter staff at branch offices must be able to cash checks for local customers.Not: "The system must be reliable."2. Interactive training materials are required such that a junior clerk, who is employed at a branch back office, can learn how to use the system in one day working independently.3. There is a computer center at the head office with 7x24 operator coverage. There are no computer staff located at the branch offices.4. The worst case for a counter transaction must be 10 seconds from when the transaction is submitted to first response.6CS 501 Spring 2003Required ReadingRequired Reading: Mitchell Kapor, A Software Design Manifesto. Dr. Dobbs Journal, 1991. http://hci.stanford.edu/bds/1-kapor.html"Software design is not the same as user interface design.""Architects, not construction engineers, are the professionals who have overall responsibility for creating buildings. ... in the actual process of designing and implementing the building, the engineers take direction from the architects."7CS 501 Spring 2003What is Design? Design is consciousDesign keeps human concerns in the centerDesign is a dialog with materialsDesign is creativeDesign is communicationDesign has social consequencesDesign is a social activityTerry WinogradBringing Design to Software, 19968CS 501 Spring 2003Progress?Examples of change: 1990 to 20039CS 501 Spring 20031990SEARCH I NSPEC Dat abase- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -Type keywor ds and pr ess RETURN - - orent er a commandDef aul t i s ADJ : aci d f r ee- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -Set #3: aci d adj f r e 0 r ecor ds I NSPEC Dat abaseSet #4: aci d adj f r ee 5 r ecor ds I NSPEC Dat abaseSet #5: aci d and paper 448 r ecor ds I NSPEC Dat abaseSet #6: deaci di f i cat i on 4 r ecor ds I NSPEC Dat abase- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -10CS 501 Spring 2003199511CS 501 Spring 2003200312CS 501 Spring 2003199513CS 501 Spring 2003200314CS 501 Spring 2003199515CS 501 Spring 2003200316CS 501 Spring 2003199517CS 501 Spring 2003200318CS 501 Spring 2003The Design/Evaluate LoopEvaluate?DesignBuildAnalyze requirements19CS 501 Spring 2003Design for UsabilityUsability of a computer system is a combination of factors:• User interface design• Functionality• Performance• Help systems and documentation• Freedom from errorsAnything else?20CS 501 Spring 2003Elements of an Interfacemetaphors: terms, images, concepts that can be learnedmental model: organization and representation of data, functions, tasks and rolesnavigation rules: how to move among data functions, activities and roleslook: characteristics of the appearance that convey informationfeel: interaction techniques that provide an appealing experienceMarcus (1993)21CS 501 Spring 2003Levels of Usabilityinterface designfunctional designdata and metadatacomputer systems and networksconceptual model22CS 501 Spring 2003The Conceptual ModelThe conceptual model is the user's internal model of what the system provides:• The desk top metaphor -- files and folders• The web model -- click on hyperlinks• The library model -- search and retrieve• The form filling model -- fill form, submitExample: The Mercury page turner23CS 501 Spring 2003Interface DesignThe interface design is the appearance on the screen and the actual manipulation by the user (look and feel) • Fonts, colors, logos, key board controls, menus, buttons• Mouse control or keyboard control?• Conventions (e.g., "back", "help")Example: Screen space utilization in the Mercury page turner24CS 501 Spring 2003Principles of Interface DesignInterface design is partly an art; there are general principles: • Consistency -- in appearance, controls, and function. • Feedback -- what is the computer system is doing? why does the user see certain results? • Users should be able to interrupt or reverse actions • Error handling should be simple and easy to comprehend • Skilled users offered shortcuts; beginners have simple, well-defined options The user should feel in control25CS 501 Spring 2003Disabilities• 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 disabilities26CS 501 Spring
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