Adapted from: The Human Factor: Designing Computer Systems for People, Rubinstein & Hersh (1984) Designers make myths. Users make conceptual models.

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1 User Interface Guidelines UI Guidelines 1 Adapted from: The Human Factor: Designing Computer Systems for People, Rubinstein & Hersh (1984) Know your users - they are not you Designers make myths. Users make conceptual models. How long does it take to learn the system (novice... expert curve) Ease of use must be designed in, not added Reliable & robust absence of malfunctions tolerance of errors protect user from harmful actions

2 UI Guidelines 2 Tailoring: accommodate individual differences w/o users having to make choices at every function. (Training wheels, user models) Productivity: using a computer should always be easier than not using a computer. Planning pays for itself many times! Software Engineering is compromise. Integrated design is design of a whole system. Separate Design from Implementation Use prototypes - evolutionary delivery to test design. Quality requires planning. Quality control is not just testing! Quality is measuring the fit of design goals to system functionality. Can you design what you can't measure?

3 Task Analysis and User Models UI Guidelines 3 20 / 80 rule Law of diminishing returns... Creeping elegance - last 20% of "perfectly complete" system takes 80% of the effort. 80 / 20 rule Put your effort where main impact will be. 20% of an application's code may do 80% of the user interface. Describe Before you Leap Who is the user? Meet the user. What tasks does the user perform now? Watch the user perform tasks.

4 Task UI Guidelines 4 How is the task learned? Learn the task. Where is the task performed? Perform task. What is the relationship between user and data? What other tools does the user have? How do users communicate w/ each other? What are the task's time constraints? Know the task! How do things go wrong? What happens when things go wrong? What work around exist? How do user currently recover? Develop an explicit use model consistent with task.

5 Develop & Use Conceptual Models UI Guidelines 5 Maintain a consisent myth. Complete, Limited Scope Systems. Have clear bounds that user can understand Visible & Distinguishable System's States. Minimize Conceptual Load. Recognize human processing limits no rules many independent terms Eliminate Mode Errors few rules many rules c o n c l e o p a t d u a l

6 Language && Relationships UI Guidelines 6 Respect the Rules of Human Conversation When people use language to interact w/ a computer they behave as if the rules of human - to - human communication apply. Respond with the Appropriate Amount and Type of Information. Data is information w/o interpretation. People are information not data processors! Numerical Information: Present what is needed, not all there is Exact data is important - use tables Relationships are important - use graphs Dimensionality should fit the data -- 3D graphs confusing

7 The User is Always Right UI Guidelines 7 The system doesn't understand the user don't condemn user - avoid "error" Incorporate spelling correctors -- minimize free text entry recognize - select > recall - generate Be Consistent in Language Use. Consistent word, grammar and style Don't anthropomorphize dialog w/ user -- wrong model of system to user System is a tool not a "friend" System should be transparent to task

8 Teach by example, not by Formalisms. UI Guidelines 8 Avoid teaching command grammars, teach command syntax through use (intuitive). Native language is learned by using and example, not by syntax and grammar. Use Application Terminology& Standard Language. Eliminate vague, poor terms. Make and use relevant metaphors Avoid complex queries. Ands can be exhaustively sequenced Ors can be sequenced w/ priority

9 Expand the Definition of Software UI Guidelines 9 Learning Aids are Part of the System Training Wheels - teaching software that can be removed latter. Tutorials designed & developed w/ system Write the User's Guide First Incorporate external myths into guide Organize on conceptual model Examples, examples, examples... An index is an Information Retrieval System

10 Guess what user wants and query if they want it. Then provide correct example (a training wheel). Help should help Help should not interfere w/ task Multiple levels of help 1 show example 2 provide "manual pages" (hyper text) 3 refer user to integrated tutorials 4 refer user to human instructors or consultants UI Guidelines 10 Prove that Help Helps Integrate help w/ error processing DWIM "do what I mean"

11 Human Interface Styles UI Guidelines 11 Avoid Multiple Style Models - Consistent UI Command Based Interface Style Punctuation shouldn't have meaning Have command line recall & editing Menu Based Interface Style Keep menus short Label menus Have consistent menu operations If large menu, have menu map (history path) & shortcuts

12 Direct Manipulation Interface Styles Respond in real time Match objects in interface w/ external myth UI Guidelines 12 Reduce homing between keyboard & pointer - provide keyboard accelerators Respond to Users Provide High Quality, Timely Response Keep users informed and comfortable have progress indicators for long tasks Acknowledge user's actions, then process Confirm user's intent not literal string. Provide easy escape, undo features

13 Error Response No surprises, don't distract. UI Guidelines 13 Handle Errors to Teach & be Productive Report errors politely, simply, and in context State errors in terms of external myth Don't blame the user Avoid error codes. Error messages should be unambiguous. Fix the problem (DWIM - training wheels) Clearly distinguish between success & error Design the Error & Help Behavior of System from the beginning

14 Integrate error recovery & help UI Guidelines 14 Response Time should be Fast and Relatively Constant Try to work in real time Have progress indicators, percent done, announce long delays, estimate how long task will take Response time is part of user's perception. Try to have response time and duration support external myth. Should "hard" tasks should take a little longer?

15 Testing Systems UI Guidelines 15 You build it, You Test it? You buiild it, others test it? Both? Specify testing & validation at design time. Have external testers also. Use subjects that are familiar w/ system or external myth (not other developers) Test User Interface w/ prototypes from screen "demo" mock-ups use representative tasks include help and error recovery Test the strength of the external myth Use an evolutionary (rapid prototyping) design w/ many deliveries exploit reusable code, object oriented tools Failures are Catastrophes not "cute" bugs...

16 Design as a reflection UI Guidelines 16 Design Model User Model designer user ideal system Design Model User Model designer user actual system

17 performance Humans learn UI Guidelines 17 Assume 3 competitive applications (A, B, and C) that exhibit these performance as a function of use functions. C B A learning and use "A" is the fastest to learn and the fastest to asymptote at a moderate level of performance. "B" is slow to learn and slow to asymptote at a low level of performance. "C" is slow to learn and slow to asymptote at a high level of performance. Are there user's appropriate for each application?

18 learning is not using UI Guidelines 18 Studies supporting consistency examine ease of learning and ease of transference from one system to another. Internal consistency reduces conceptual load External consistency reduces training Assumes that easy to learn is easy to use... However, Humans are fast learners, but learning is hard Systems are acquired to use for increased productivity not for learning Skilled performance is important, may require learning Training Wheels, incorporate learning into beginning user model, monitor performance and remove training wheels from UI

19 Case against Interface Consistency J. Grudin, CACM, 1989 UI Guidelines 19 Consistency is a major watch word in guides for developing good user interfaces. Consistency!= perceived consistency 3 Types of Consistency 1. Internal Consistency. Easily controlled by the design team. Command language 2. User Interface Consistency. Externally consistent with environment or desktop. -- User Interface controls menus, buttons, dialogs Tool / Analogy Consistency. Consistent with a model, analogy, or external tool. -- Remote monitoring & physical gauges

20 Consistency is One of Many Goals UI Guidelines 20 Intensive task use analysis of users is vital to user interface design. Consistency can be centered on: what is most often done what did the user do last what would the user do next 1 Grudin's Arrow Keys 2 3 Which is better? 1 more consistent with external analogy - correction is opposite key 2 best performance + easy correction, multi-fingered use

21 Thinking Fast & Slow Two cognitive human decision making systems: UI Guidelines 21 System 1: automatic, unconscious, approximate, easy, visual, emotional / sensational, fast System 2: conscious, deliberate, rational, precise, difficult, verbal, slow Most decisions are made with system 1 (default system) Important decisions should be made with system 2. Tversky & Kahneman, Judgment under Uncertainty: Heuristics and Biases, 1974 Psychology of decision making Behavioral Finance Losses > Gains risk averse but like to gamble and take risks Sensational, Memorial > Statistics, Factual fears flying, prefers to drive good story, familiar source rather that facts

22 System 2 applications UI Guidelines 22 Decision Support Systems (DSS) tools for System 2 Provide all options. But don t overwhelm, organize options, provide summary thumbnails information Facilitate alternatives. Expose users to non-intuitive alternatives, help discovery of decisions. Information based. Provide unbiased data w/o requirement for calculation. Perform deductions (show steps if asked), provide inferences. (minimize system 2.) Transparent working. Explain assumptions and results with examples, memorial stories. (play to system 1.)

23 System 1 applications UI Guidelines 23 Persuasive applications sweets for System 1 Make a quick, impulsive, self-satisfying decision Charities, Advertisers, Political/religious recruiters Visual, emotional images: fear, pleasure, status Exploiting System 1 for the greater good How to increase system updates, backups, redundant storage?