conceptual models of interaction (Human Computer interaction)
- 4. ◾ Model of a system = how it works its constituent parts and how they work together to do what the system does ◾ Implementation models Pixel editing (Photoshop) vs. structured graphics (Visio)
- 5. ◾ Three models are relevant to UI design: Model that the system How system works presents to the user through its user interface How the user thinks the system works
- 6. ◾ Interface model might be quite different from the system model ◾ Interface model should be: simple ▪hides system model more closely reflect the user’s model of the actual task ▪which you can learn from task analysis
- 7. ◾ The user’s model may be totally wrong without affecting the user’s ability to use the system ◾ Sometimes harmless Electricity as water ◾ Sometimes misleading Thermostat as a valve
- 8. ◾ Learnability is one of the major goals of usability ◾ Command language ◾ Menus & forms ◾ Direct manipulation
- 9. ◾ User types in commands in an artificial language ls -l *.java Unix shell ww w. cs .r u. ac .z
- 10. ◾ User is prompted to choose from menus and fill in forms
- 11. ◾ Shneiderman (1983) coined the term Direct Manipulation (conceptual model) ◾ Came from his fascination with computer games at the time ◾ Proposes that digital objects be designed so they can be interacted with analogous to how physical objects are manipulated ◾ Assumes that direct manipulation interfaces enable users to feel that they are directly controlling the digital objects
- 12. ◾ Continuous representation of objects and actions of interest representation may be verbal (words) or iconic (pictures), but it’s continuously displayed, not displayed on demand ▪e.g. icons representing files ◾ Physical actions and button pressing instead of issuing commands with complex syntax physical actions are the most direct kind of actions - clicking or dragging ◾ Rapid reversible actions with immediate feedback on object of interest ◾ It exploits perceptual and motor skills of the human machine
- 13. ◾ Novices can learn the basic functionality quickly ◾ Experienced users can work extremely rapidly to carry out a wide range of tasks, even defining new functions ◾ Intermittent users can retain operational concepts over time ◾ Error messages rarely needed ◾ Users can immediately see if their actions are furthering their goals and if not do something else ◾ Users experience less anxiety ◾ Users gain confidence and mastery and
- 14. ◾ Some people take the metaphor of direct manipulation too literally ◾ Not all tasks can be described by objects and not all actions can be done directly ◾ Some tasks are better achieved through delegating rather than manipulating e.g., spell checking ◾ Moving a mouse around the screen can be slower than pressing function keys to do same actions
- 15. ◾ Learnability - knowledge in the head vs. world CL significant earning, MF and DM more information in world ◾ Error messages CL and MF have error messages, DM none ◾ Efficiency CL very efficient for experts, MF needs good shortcuts, DM only if it is correct ◾ User experience CL for expert users, MF and DM for novices and infrequent users ◾ Synchrony CL and MF synchronous, DM asynchronous ◾ Programming difficulty CL relatively easy, MF easy, DM hardest ◾ Accessibility CL & MF easier for screen readers than DM
- 16. ◾ Don Norman’s book: “Design of Everyday Things” affordances natural mapping visibility feedback
- 17. ◾ Perceived and actual properties of a thing that determine how the thing could be used Chair is for sitting Doorknob is for turning Button is for pushing Listbox is for selection Scrollbar is for continuous scrolling or panning ◾ Affordances are how an interface communicates nonverbally with the user ◾ Perceived vs. actual affordance ◾ UI should agree in perceived and
- 24. ◾ A design solution based on a natural mappings reduces the need for additional explanatory information in memory ◾ Physical arrangement of controls should match arrangement of function ◾ Best mapping is direct, but natural mappings don’t have to be direct Light switches Stove burners Turn signals
- 25. ◾ Relevant parts of system should be visible not usually a problem in the real world but takes extra effort in computer interfaces ◾ Availability of drag & drop is often invisible
- 26. ◾ Actions should have immediate, visible effects Push buttons Scrollbars Drag & drop ◾ Kinds of feedback Visual Audio Haptic
- 27. ◾ Low-level feedback e.g. push button ◾ High-level feedback model state changes new web page starts loading
- 28. ◾ Conceptual model designed to be similar to a physical entity but also has own properties e.g. desktop metaphor, search engine ◾ Exploit user’s familiar knowledge, helping them to understand ‘the unfamiliar’ ◾ Conjures up the essence of the unfamiliar activity, enabling users to leverage of this to understand more aspects of the unfamiliar functionality ◾ People find it easier to learn and talk about what they are doing at the computer interface in terms familiar to them
- 29. ◾ Makes learning new systems easier ◾ Helps users understand the underlying conceptual model ◾ Can be innovative and enable the realm of computers and their applications to be made more accessible to a greater diversity of users
- 30. ◾ Ted Nelson (1990) identifies these problems: Break conventional and cultural rules ▪ e.g., recycle bin placed on desktop Can constrain designers in the way they conceptualize a problem space Conflict with design principles Forces users to only understand the system in terms of the metaphor Designers can inadvertently use bad existing designs and transfer the bad parts over Limits designers’ imagination in coming up with new conceptual models ◾ Rule of thumb: use it if you have one, but don’t stretch for one if you don’t