Presentation on theme: "(Introduction, Part 2) Fall 2008"— Presentation transcript:
1 (Introduction, Part 2) Fall 2008 CS305, HCI in Software Development Usability Goals, Principles, Guidelines(Introduction, Part 2)Fall 2008
2 Activity (Mini-Homework) Do this on your own on in pairsGo find two examples of problems in the GUIs of software apps or the UI of a interactive device (not Web pages)Problem must illustrate a violation of one of the design principles or usability guidelinesDescribe the problems in these terms“Post” on Collab wiki page before class next Fri.
3 Reminder….users should be involved through the development of the projectspecific usability and user experience goals need to be identified, clearly documented and agreed at the beginning of the projectiteration is needed through the core activities
4 Towards More Usable Systems Seems like we need the following:Goals we want to achievePrinciples on how to achieve theseLists of do’s and don’tsTheories that underlie principles, listsMethods for measuring and evaluating
5 Usability Goals Here’s one set (from the ID textbook) Effective to use Efficient to useSafe to useHave good utilityEasy to learnEasy to remember how to use
6 Usability Goals Effective to use (effectiveness) A general goal: how well does a system do what it should do?Efficient to use (efficiency)Do things quickly, easily.Especially common tasks.Safe to use (safety)Protect people from hazards (usually not a SW issue)Help prevent user from making errors and recover from errorsGive users confidence
7 Usability Goals (2) Have good utility Easy to learn (learnability) Has the right kind of functionalitySupports users in accomplishing tasksEasy to learn (learnability)Includes how easy it is to learn advanced features. (If hard, who bothers?)Easy to remember how to use (memorability)Many systems used infrequently
8 How to Measure Usability? We want to achieve these goals, but how do we know?Develop measurable criteria based on previous goals. Examples:Time to learnSpeed of performanceRate of errors over by usersRetention over timeSubjective satisfaction
9 User experience goals Satisfying - rewarding Fun - support creativity Enjoyable - emotionally fulfillingEntertaining …and moreHelpfulMotivatingAesthetically pleasing
10 Usability and user experience goals How do usability goals differ from user experience goals?How easy is it to measure usability versus user experience goals?Are there trade-offs between the two kinds of goals?e.g. can a product be both fun and safe?
12 Reminder of where we are Usability GoalsSome measuresUser Experience GoalsDesign PrinciplesFirst two were higher level (goals)Now talking about guidance for how to achieve goalsGuidelines (guidance as lists)
13 Design principlesGeneralizable abstractions for thinking about different aspects of designThe do’s and don’ts of interaction designBut at a high level. (Compare to guidelines later.)What to provide and what not to provide at the interfaceDerived from a mix of theory-based knowledge, experience and common-sense
14 Higher-level Principles Now, we’ll talk about the following:VisibilityFeedbackConstraintsMappingConsistencyAffordancesIdeas well-known (e.g. from Norman’s Design of Everyday Things)
15 Activity (Mini-Homework) Do this on your own on in pairsGo find two examples of problems in the GUIs of software apps or the UI of a interactive device (not Web pages)Problem must illustrate a violation of one of the design principles or usability guidelinesDescribe the problems in these terms“Post” on Collab wiki page before class next Fri.
16 Visibility • This is a control panel for an elevator. • How does it work?• Push a button for the floor you want?• Nothing happens. Push any other button? Still nothing. What do you need to do?It is not visible as to what to do!From:
17 Visibility…you need to insert your room card in the slot by the buttons to get the elevator to work!How would you make this action more visible?make the card reader more obviousprovide an auditory message, that says what to do (which language?)provide a big label next to the card reader that flashes when someone entersmake relevant parts visiblemake what has to be done obvious
18 Feedback Sending information back to the user about what has been done Includes sound, highlighting, animation and combinations of thesee.g. when screen button clicked on provides sound or red highlight feedback:“ccclichhk”
19 Constraints Restricting the possible actions that can be performed Helps prevent user from selecting incorrect optionsThree main types (Norman, 1999)physicalculturallogical
20 Physical constraintsRefer to the way physical objects restrict the movement of thingsE.g. only one way you can insert a key into a lockHow many ways can you insert a CD or DVD disk into a computer?How physically constraining is this action?How does it differ from the insertion of a floppy disk into a computer?
21 Logical constraintsExploits people’s everyday common sense reasoning about the way the world worksAn example is the logical relationship between physical layout of a device and the way it worksSee next slide for an illustration
22 Logical or ambiguous design? Where do you plug the mouse?Where do you plug the keyboard?top or bottom connector?Do the color coded icons help?From:
23 More Logically Constrained Provides direct adjacent mapping between icon and connectorProvides color coding to associate the connectors with the labelsFrom:
24 Cultural constraintsLearned arbitrary conventions like red triangles for warningCan be universal or culturally specificFor SW we’ve accepted certain conventions, e.g. we know what to do with an iconBe concerned of cross-cultural conventions and other ambiguities!Does an “X” mean “selected” or “not selected”Is a check-mark better?
25 Which are universal and which are culturally-specific?
26 MappingRelationship between controls and their movements and the results in the worldWhy is this a poor mapping of control buttons?
27 Mapping Why is this a better mapping? The control buttons are mapped better onto the sequence of actions of fast rewind, rewind, play and fast forwardIs this a logical mapping (in most people’s minds)?Is there a mapping that makes more sense?
28 Mappings in the Kitchen Which controls go with which rings (burners)?ABCD
30 ConsistencyDesign interfaces to have similar operations and use similar elements for similar tasksFor example:always use ctrl key plus first initial of the command for an operation – ctrl+C, ctrl+S, ctrl+OMain benefit is consistent interfaces are easier to learn and useBut… didn’t a wise man say this? Consistency is the hobgoblin of little minds.A foolish consistency is the hobgoblin of little minds (adored by little statesmen and philosophers and divines)Quote from Ralph Waldo Emerson, Self-Reliance
31 When consistency breaks down What happens if there is more than one command starting with the same letter?e.g. save, spelling, select, styleHave to find other initials or combinations of keys, thereby breaking the consistency ruleE.g. ctrl+S, ctrl+Sp, ctrl+shift+LIs this desirable? Does it defeat the purpose?It may increase learning burden on userIt may make them more prone to errorsBut it may still benefit frequent or experienced users
32 Internal and external consistency Internal consistency refers to designing operations to behave the same within an applicationDifficult to achieve with complex interfacesExternal consistency refers to designing operations, interfaces, etc., to be the same across applications and devicesVery rarely the case, based on different designer’s preferenceMost successful in product families (e.g MS Office)Op. Sys. vendors may define style guidelines
33 Keypad numbers layout A case of external inconsistency (a) phones, remote controls(b) calculators, computer keypads123789456456789123
34 Affordances: to give a clue Refers to an attribute of an object that allows people to know how to use itE.g. a mouse button invites pushing, a door handle affords pullingNorman (1988) used the term to discuss the design of everyday objectsSince then has been popularized in interaction design to discuss how to design interface objectsE.g. scrollbars to afford moving up and down, icons to afford clicking on
35 What does ‘affordance’ have to offer interaction design? Notion of affordance is often over-used!Interfaces are virtual and do not have affordances like physical objectsNorman argues it does not make sense to talk about interfaces in terms of ‘real’ affordancesInstead interfaces are better conceptualised as ‘perceived’ affordancesLearned conventions of arbitrary mappings between action and effect at the interfaceSome mappings are better than others
36 Activity 1.3 Physical affordances: How do the following physical objects afford? Are they obvious?
37 Activity 1.4 Virtual affordances How do the following screen objects afford?What if you were a novice user?Would you know what to do with them?
38 Activity 1.5: Physical and Perceived Affordances Take a cell phone, digital camera, or PDAHave laptop? Open a fancy SW app: Outlook, Eclipse, etc?In a small groupIdentify any physical affordances the device hasIdentify any perceived or visual affordances the software user interface hasWrite these down, be prepared to share or turn in
40 Adjusting Tabs in MS Word What’s the idea here? Problems?What principle(s)?AffordanceMetaphor (more on this later)
41 Web Links What are the conventions that help you recognize a link? Would you are argue this is an affordance?A perceived affordance – convention of a mapping between action and effectDoes it “afford” clicking on it?Examples of problems with this?Let’s look at:Underline is the convention.Changes color when hover overchanges after visitedAlso graphics images (sometimes)Sometimes not underlinedBold text (but not all bold)Sometimes buttons
44 Overview (Reminder) Guidelines Usability Goals User Experience Goals Design PrinciplesGuidelinesStill talking about guidance for how to achieve goalsThese are more prescriptive (do’s & don’ts)
45 Guidelines What do we mean by “guidelines”? Tell me!Are guidelines enough? Lead to problems?Too specific, incomplete. Don’t generalize to all situationsBut… Capture experience and best practicesMany examples of guidelines…
46 Nature of GuidelinesSimilar to design principles, except more prescriptiveUsed mainly as the basis for evaluating systemsProvide a framework for heuristic evaluationWe’ll talk about particular approach to evaluation this later
47 Jakob Nielsen Says… Jakob Nielsen: a leading figure in usability Member of the Nielsen Norman GroupDonald NormanBruce "Tog" TognazziniAlertbox: regular “column”Wikipedia:
48 “Usability principles” (Nielsen 2001) Visibility of system statusMatch between system and the real worldUser control and freedomConsistency and standardsHelp users recognize, diagnose and recover from errorsError preventionRecognition rather than recallFlexibility and efficiency of useAesthetic and minimalist designHelp and documentation
49 Read More about Nielsen’s List(s) Nielsen’s site has more on the previous listHeuristics: more general “guidelines”We’ll see this term againHeuristic evaluationActivity 1.7 for you to do:Find one list of similar usability principles (i.e heuristics, prescriptive guidelines, do’s/don’ts) for Web page designWrite it down – we’ll collect these
50 Shneiderman’s Eight Golden Rules Strive for consistencyCater to universal usabilityOffer informative feedbackDesign dialogs to yield closurePrevent errorsPermit easy reversal of actionsSupport internal locus of controlReduce short-term memory load.
51 More Specific Guideline Examples from DTUI Shneiderman’s text (DTUI) gives some more detailed examplesNational Cancer Institute, p. 62W3C, Accessibility, p. 62Display organization, p. 63Control rooms, p. 63Others in Section 2.2Ask yourself: what principle(s) underlie each guideline?
52 Ex. 1: National Cancer Institute 388 guidelines for informative web pages, such as:Reduce user’s workloadDo not display unsolicited windows or graphicsStandardize task sequencesEnsure embedded links are descriptiveUse unique and descriptive headingsDevelop pages that print properlyUse thumbnail images to preview large images
53 Ex. 2a, Organizing Data Display From Smith and Mozier (1986).Data display: 5 high-level goalsConsistency of data displayEfficient information assimilation by the userMinimal memory load on the userCompatibility of data display with data entryFlexibility for user control of data displayData entry: 5 similar high-level goals, but also:Minimal input actions by user
54 Ex. 2b, More Specific than 2a Lockheed (1981) on control roomsBe consistent in labeling, graphics, formattingStandardize abbreviationsPresent data only if it assists the operatorPresent data graphically where appropriate instead of numbers and textRely on monochromatic displays with good spacing and arrangement, saving color for when it helpsInvolve users in development of displays
56 Activity (Mini-Homework) Do this on your own on in pairsGo find two examples of problems in the GUIs of software apps or the UI of a interactive device (not Web pages)Problem must illustrate a violation of one of the design principles or usability guidelinesDescribe the problems in these terms“Post” on Collab wiki page before class next Fri.