Apple over het gebruik van metaforen in interfaces

Metaforen in interfaces

Het stijlboek van Apple voor het interface-ontwerp (van de iPhone) heeft als ondertitel User experience. Gaat het nu om Usability of om User Experience?

In een recent artikel betoogt Owen [1] dat deze twee invalshoeken elkaar weliswaar niet uitsluiten, maar dat er wel degelijk een belangrijk onderscheid gemaakt moet worden.

Usability refers to the ease with which a user can accomplish his or her goals using any tool.


Somewhat in contrast, user experience refers to the way a user perceives his or her interaction with a system.

Als je twee labels voor deze concepten zou kiezen, dan gaat het volgens Owen om Science (usablity design) versus Art (user experience design):

Perhaps the simplest way to distinguish the two would be to summarize them as “art” and “science”, with usability representing science, though I caution you to use this callous and unrefined description sparingly and certainly not within ear shot of opinionated practitioners of either field, as it is sure to cause a (not wholly unjustified) rant. Yet the distinction is not without merit – user experience is often far more concerned with subjective artistry, and the emphasis on data crunching and numbers in true usability research is surely scientific. At the end of the day all that is really important is to understand the distinction between the two terms and to realize the massive importance of both in the design of good interfaces.

Hoe combineert Apple usability en user experience?

Nadat het principe van User Centered Design nog eens is benadrukt  (“a great user interface follows human interface design principles that are based on the way people – users – think and work, not on the capabilities of the device.”) vinden we in de iPhone Human Interface Guidelines, in het hoofdstuk Human Interface Principles: Creating a Great User Interface zes aandachtspunten:

  • Metaphors: when possible, model your application’s objects and actions on objects and actions in the real world.
  • Direct Manipulation: people feel they are controlling something tangible, not abstract. The benefit of following the principle of direct manipulation is that users more readily understand the results of their actions when they can directly manipulate the objects involved. iPhone OS users enjoy a heightened sense of direct manipulation because of the Multi-Touch interface. Using gestures, people feel a greater affinity for, and sense of control over, the objects they see on screen.
  • See and Point: by presenting choices or options in list form, so users can easily scan them and make a choice. Keeping text input to a minimum frees users from having to spend a lot of time typing and frees your application from having to perform a lot of error checking.
    Presenting choices to the user, instead of asking for more open-ended input, also allows them to concentrate on accomplishing tasks with your application, instead of remembering how to operate it.
  • Feedback: your application should respond to every user action with some visible change. For example, make sure list items highlight briefly when users tap them. Audible feedback also helps, but it can’t be the primary or sole feedback mechanism because people may use iPhone OS–based devices in places where they can’t hear or where they must turn off the sound.
  • User Control: allow users, not your application, to initiate and control actions. Keep actions simple and straightforward so users can easily understand and remember them. Whenever possible, use standard controls and behaviors that users are already familiar with.
  • Aesthetic Integrity: aesthetic integrity is not a measure of how beautiful your application is. It’s a measure of how well the appearance of your application integrates with its function.

When possible, model your application’s objects and actions on objects and actions in the real world.This technique especially helps novice users quickly grasp how your application works. Folders are a classic software metaphor. People file things in folders in the real world, so they immediately understand the idea of putting data into folders on a computer.

Metaphors in iPhone OS include iPod playback controls, tapping controls to make things happen, sliding on-off switches, and flicking through the data shown on picker wheels. Although metaphors suggest a use for objects and actions in the iPhone OS interface, that use does not limit the software implementation of the metaphor.

Bijvoorbeeld Apple’s iBook applicatie op de iPad:

Boekenkast en/of tijdschriftplanken als metafoor voor e-books en e-magazines

Toelichting bij het gebruik van metaforen:

As you design your application, be aware of the metaphors that exist in iPhone OS and don’t redefine them. At the same time, examine the task your application performs to see if there are natural metaphors you can use. Bear in mind, though, that it’s better to use standard controls and actions than to stretch a real-world object or action just to fit your application’s user interface. Unless the metaphors you choose are likely to be recognized by most of your users, including them will increase confusion instead of decrease it.

Conclusie: in een goede interface

  • is het design user centered
  • gaan usability design en user experience design hand in hand; ze zijn naadloos geïntegreerd


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