Design Rule lect07.ppt Human Computer Interaction
- 1. Design Rules
- 2. DESIGN RULES Designing for maximum usability – the goal of interaction design • Principles of usability – general understanding • Standards and guidelines – direction for design • Design patterns – capture and reuse design knowledge
- 3. TYPES OF DESIGN RULES • principles – basic principles of design: contrast, balance, importance, amount, hierarchy, repetition, rhythm, pattern, white space, movement, variety, and unity. – These visual and graphic design principles work together to create appealing and functional designs that make sense to users.
- 4. • standards – specific design rules – high authority – limited application – provide direction for design, in both general and more existing terms, in order to improve the interactive properties of the system.
- 5. • Guidelines • Basic design guidelines include principles like consistency, simplicity, usability, accessibility, and visual hierarchy. • These principles, standard and guidelines are help ensure that designs are user-friendly, aesthetical pleasing, and functional.
- 6. Principles to support usability Learnability the simplicity with which new users can begin effective interaction and achieve maximal performance Learnability refers to how simple it is for an application end-user to pick up, understand and use the program. Flexibility the multiplicity of ways the user and system exchange information Flexibility is the availability of multiple interaction methods between the user and the system
- 7. Robustness(rebasnes) the quality or condition of being strong and in good condition. the level of support provided the user in determining successful achievement and assessment of goal- directed behaviour Robustness is the degree of assistance offered to the user in assessing goal-directed behavior and successfully identifying system performance
- 8. Principles of learnability Learnability principles are concerned with interactive system features, which assist beginner users to learn quickly and also allows stable sequence to expertise. Predictability – determining effect of future actions based on past interaction history – operation visibility is concerned with showing the availability of operations which can be performed next by the user – This interactive design principle requires a user's knowledge of interaction to be sufficient to determine the outcome of present or future interaction with the system.
- 9. Synthesizability – assessing the effect of past actions – It determines the effects of past operations on current states. eg. - move file. – Familiarity: New users can get familiar with the functionality and interaction style of the application – In general, these principles relate to the ability of the interactive system to provide the user with an observable and informative notification about the operation state changes within the system. – immediate vs. final integrity
- 10. Principles of learnability (ctd) Consistency – likeness in input/output behaviour arising from similar situations or task objectives – Standard GUI design factors should aid designers to take into account consistency at every level, and, "look and feel" issues should never be discarded. The use of labels and icons should always be consistent and the same icons and labels should mean the same thing
- 11. Familiarity – how previous knowledge applies to new system – either real world or gained from interaction with other systems, onto the features of a new system. – The appearance of an object provides familiarity with its behaviour. Effective use of appearance in an interactive system design can improve the familiarity of the system. – guessability; affordance – the quality or property of an object that defines its possible uses or makes clear how it can or should be used.
- 12. Generalizability – extending specific interaction knowledge to new situations – This interactive design principle provides support for users to extend knowledge of specific interaction within, and across applications, to new, but similar situations. For example, cut/copy/paste operations within Microsoft Office applications use of same short- cut keys.
- 13. Principles of flexibility Flexibility in interactive design extends the way a user and the system exchange information. By applying flexibility principles to an interactive system design, designers aim to improve a system's usability. Dialogue initiative – When the system controls the dialog flow, the dialog is said to be system preemptive/defensive. – Conversely, when the flow is controlled by the user, the dialog is said to be user preemptive. – In general a user preemptive dialog is special although some situations require a system preemptive dialog. – In reality some line between these two extremes is usually the most satisfactory solution.
- 14. Multithreading – Multi-threading within a interface provides support for multiple tasks to be performed at one time. – Multi-threading within an interface allows for the execution of numerous processes simultaneously. – An interleaved system allows working on a single task at a time. For example, a word processor enables numerous documents to be open, but only one can be performed at any given moment. – A concurrent system allows numerous processes to be performed simultaneously. For example, while browsing, one can stream, search, and download concurrently.
- 15. Task migratability – passing responsibility for task execution between user and system A computerized spell checker is a good example to this. •It is a waste of time for a user to verify and correct a lengthy document manually. Allowing a spell-checker program to perform this operation without the user's assistance is deemed dangerous.
- 16. Principles of flexibility (ctd) Substitutivity Substitutivity offers a user alternative ways of specifying input or viewing output. Indeed the distinction between output and input can be unclear. (values in input eg fractions/decimals, values in output eg both digital and analog, output/input eg output can be reused as input). – representation multiplicity; equal opportunity – The extent to which an application permits equivalent input and output values to be substituted for each other is referred as substitutivity.
- 17. Customizability – In order to meet the user's needs, customization refers to the user interface modification by the system or the user. – There are two forms of customization: – Adaptability means the ability of the user to modify the interface in accordance with their requirements. – Adaptivity refers to the system's capacity to alter the interface based on the user's needs by identifying them as beginner or expert.
- 18. Principles of robustness Observability – ability of user to evaluate the internal state of the system from its identify representation – If a user cannot understand the internal state of the system, there is a high likelihood that the user's confidence will be very low, – browsability; defaults; reachability; persistence; operation visibility – if the system is performing a time consuming operation, the current status of the operation should be displayed - a web browser will indicate the on- going status of a page download.
- 19. Recoverability – ability of user to take corrective action once an error has been recognized – Users should be able to reach a desired goal after recognition of errors in previous interaction. – Error recovery can be achieved in two ways, – forward (negotiation) and backward (undo). – Forward error recovery involves a user accepting the current state of the system and negotiating from the present state towards the required state. – A backward error recovery mechanism within a system allows a user to undo the undesired outcome of the previous interaction by returning to a previous state.
- 20. Principles of robustness (ctd) Responsiveness – how the user recognize the rate of communication with the system – Stability – Response time, indicating change of states within the system, is important. Short duration or instantaneous response time is more desirable.
- 21. Task conformance – degree to which system services support all of the user's tasks There are two aspects of task conformance, – task completeness, and task adequacy. – Task completeness is concerned with whether a system is capable of supporting the entire task that a user wishes to perform. – The task adequacy(the testing procedures) is concerned with addressing the user's understanding of these tasks It is necessary that an interactive system should allow the user to perform the desired tasks as defined during the task analysis.
- 22. Standards • set by national or international bodies to ensure compliance by a large community of designers standards require sound underlying theory and slowly changing technology • hardware standards more common than software high authority and low level of detail • ISO 9241 defines usability as effectiveness, efficiency and satisfaction with which users accomplish tasks
- 23. Guidelines • a general rule, principle, or piece of advice • more suggestive and general • many textbooks and reports full of guidelines • abstract guidelines (principles) applicable during early life cycle activities • detailed guidelines (style guides) applicable during later life cycle activities • understanding justification for guidelines helps in resolving conflicts
- 24. Golden rules and heuristics • “Broad brush” design rules • Useful check list for good design • Better design using these than using nothing! • Different collections e.g. – Nielsen’s 10 Heuristics (see Chapter 9) – Shneiderman’s 8 Golden Rules – Norman’s 7 Principles
- 25. Shneiderman’s 8 Golden Rules 1. Strive/struggle for consistency 2. Enable frequent users to use shortcuts 3. Offer informative feedback 4. Design dialogs to yield closure 5. Offer error prevention and simple error handling 6. Permit easy reversal of actions 7. Support internal locus of control 8. Reduce short-term memory load
- 26. 1.Strive For Consistency: • Consistency can be achieved through elements such as fonts, color, shape, and position being consistently the same in all menus & screens, across, categories for a particular software. • The sequence of actions that we perform must be in a similar situation. • Usage of Identical terminology in prompts, menus, screens, capitalization, fonts, and layouts must be consistent throughout. • Users should be able to do the same thing in the same way that they have been doing every time. • consistency such as similar sequences of actions in similar situations makes it easy to learn. • There should be a limited number of exceptions regarding the echoing of passwords and commands.
- 27. 2. Enable frequent users to use shortcuts • Seek Universal Usability: • The enable frequent users rule recognizes that experienced users often want to work more efficiently and may prefer to use shortcuts to perform frequent and minor actions more quickly. • Designers should provide shortcuts to frequently used actions or functions that experienced users can learn and use to increase their productivity. Shortcuts can be achieved through keyboard shortcuts, mouse gestures, or other input mechanisms that allow users to bypass menus and dialogue boxes. • While designing make sure you keep in mind various audiences ranging from different expertise, ages, disabilities, and international variations. • Introduction of shortcuts for faster pacing and user interactions.
- 28. 3. Offer informative feedback • Proper feedback should be provided for every user action. For frequent actions, the response can be modest whereas for infrequent actions the response can be substantial. • Interfaces not just being communicative but also need to help users in terms of learning and feedback which tells them that they are moving in the right direction. • Feedback can be in the form of visual, auditory, or physical responses, and it should provide users with clear and timely information about the results of their actions. Informative feedback helps users feel more in control and confident while interacting with the system, reduces uncertainty and errors, and enhances the overall user experience.
- 29. 4. Design dialogs to yield closure • Designers should design dialog boxes that clearly state the purpose of the dialog and provide clear and concise information to the user. • The dialog should be designed in a way that enables the user to make a decision or complete a task, and it should provide clear feedback about the outcome of the action taken. • Interaction dialogue needs to have a closure that is recognized by the user as the end of an action. • The sequence of actions needs to proceed in a dialogue by engaging the user in a step-by-step manner.
- 30. 5. Offer error prevention and simple error handling • Error handling is an essential aspect of user interface design since it is impossible to create a system that is completely error-free. Therefore, it is crucial to design error messages that are clear, concise, and provide enough information to help the user resolve the issue. • Make sure the user interface is as user-friendly as possible. such that user doesn’t make any serious errors. • Users can commit errors while interacting with the computers as well as while inputting or interpreting information. • If the user commits an error the interface should offer simple, constructive, and specific instructions for recovery.
- 31. 6. Permit easy reversal of actions • The interactions must be built such that retracing backward or reverse of actions can be performed which gives flexibility to users to explore new options. • Make sure the actions are as much as reversible. such that user doesn’t feel anxiety, as the user knows that errors can be undone, and helps the user to explore unfamiliar options. • The system should encourage exploration without incurring any kind of anxiety for users. • one way to do this is to provide a noticeable path backward of all actions. • Reversibility may be single action such as a data entry task or a group of actions such as the entry of name and address.
- 32. 7. Support internal locus of control locus is particular position or place where something occurs or is situated. • Designers should design interfaces that allow users to easily navigate and interact with the system. • Users should be able to start, pause, or stop a process at any time, and the system should respond quickly and predictably to their actions. • Allow users to always feel ‘in control’ of the system and of the situation. Make the user aware that he/she is in control. • Users should believe that they are controlling the system and not the way around. • Users should never feel lost. • Experienced users don’t like it If any new features are added to the interface as it makes them feel new and uncomfortable. • Changes in familiar behavior make users angry and make them unable to produce a desirable result.
- 33. 8. Reduce short-term memory load • As Humans have a limited capacity for Information processing in short- term memory. • Designers should design interfaces that provide clear and concise instructions, labels, and feedback, so users don't have to rely on their short-term memory to remember what they need to do next. • This can be achieved through the use of consistent and meaningful icons, clear and concise language, and well-organized layouts that guide users through the process. • The interface design must be in such a way that it should not force users to remember huge amounts of information which make them overwhelmed like remembering information from one display and then using it on another display • Overwhelmed have a strong emotional effect .
- 34. Norman’s 7 Principles 1. Use both knowledge in the world and knowledge in the head. 2. Simplify the structure of tasks. 3. Make things visible: bridge the gulfs of Execution and Evaluation. 4. Get the mappings right. 5. Exploit the power of constraints, both natural and artificial. 6. Design for error. 7. When all else fails, standardize.
- 35. 1. Use both knowledge in the world and knowledge in the head. • Knowledge in the head is memory. Knowledge in the world is everything else — external information. • This is the knowledge in the head. It is our memory of arbitrary/random things , events or memory through explanation. • Knowledge in the world is something we do not need to remember things, or even understand them particularly well, to shuffle about with the things before us and try to figure out how to get what we work.
- 36. • Knowledge in the world is willingly available to the user. Knowledge in the head is internalized knowledge. • Effective design that assists users capitalizes on both external indication in the world and internal user knowledge.
- 37. 2. Simplify the structure of tasks. • Eliminate or restructure complexities, minimizing the planning and problem solving a task requires. • Short term memory limits people to about five unrelated items at a time. Long term memory is limited by accessibility. • To reduce the load on a user's memory, if tasks are similar, keep them similar. • Provide external indication to help the user. Make the task and feedback visible to the user so they understand their place in the process and maintain control.
- 38. 3. Make things visible: bridge the gulfs of Execution and Evaluation • Evaluation: Understanding the state of the system. • Execution: Taking action to achieve a specific goal • When users execute an action, keep it visible so that they have feedback on their action. Keep things visible when users are evaluating so that they can tell the effects of their actions. • Designers should make things visible on the execution side so that users know what to do and how to do it. • To really bridge the gulfs/gap, the system should have good interfaces that facilitate the interaction between the users and computers more efficiently.
- 39. 4. Get the mappings right • Users expect execution and evaluation to naturally map to something they know. Help the user determine these relationships: • Between intentions and possible actions • Between actions and effects • The state of the system by sight, sound, or feel • The state of the system as it relates to the user's needs, intentions, and expectations
- 40. 5. Exploit the power of constraints, both natural and artificial • Help the user do only one thing--the the thing they are trying to do, the goal they are hoping to complete. • Use constraints so that the user feels as if there is only one possible thing to do – the right thing of course • both natural and artificial. Constraints are things in the world that make it impossible to do anything but the correct action in the correct way
- 41. 6.Design for error • To err is human, so expect the errors the user could make and design recovery into the system. • Anything that can go wrong, will" is useful to keep in mind when considering how users engage with a system. Prepare to support user's actions, not fight against them. Help users recover from errors.
- 42. 7.When all else fails, standardize • When natural mappings are difficult or impossible, standardize actions, outcomes, layouts, and displays for predictability and consistency. • Facilitating user success should be a top priority for designers. • Norman's principles hold designers responsible for helping users understand what to do with a system and providing visibility into the system's current state.
- 43. HCI design patterns (cont.) • Characteristics of patterns – capture design practice not theory – capture the essential common properties of good examples of design – represent design knowledge at varying levels: social, organisational, conceptual, detailed – represent values and can express what is humane in interface design – are perceptive and readable and can therefore be used for communication between all stakeholders – a pattern language should be generative and assist in the development of complete designs.