Interface Design - tips, resources and ranting

The interface design process

1. Draw up a list of everything that the system is required to do. In reality this is very hard to do, as nearly everything evolves as work progresses. However, it's still very useful to have an initial specification. Even if it goes to pot very quickly, the process of creating it alone can be useful.
    
2. Analyse the requirements of your typical users, usually by surveying the intended users and their peers.
    
3. Design the information architecture -- the way that processes and information flow within the system. This is a very important step that is often missed completely.
    
4. Prototype design. Prototypes are often designed on paper or in a very stripped down interactive form. Again, this step is often missed and it shouldn't be!
    
5. Rigorous usability testing. This is done with a real user or users (the more the merrier). This one is important enough that I could say it several times. Even showing it to one person (e.g. your mum) can give you really valuable insight. Needless to say, importance is often inversely proportional to how often a task gets done...
    
6. Design how the interface will look in its final version. Once all the functional elements are operational, the information is organised and the usability has been tested, it is time to create the interface itself. Depending on the software, to create a unique look and feel, a graphic designer might be involved at this stage and custom icons may be created.

Concepts in interface design

• Learnability
  How quick is it to learn an interface? How easy? Many of us have been given a few seconds pause in front of an automatic ticket dispenser or cash machine from time to time, and some of us are still struggling years later with our computers.
  
  In general, an interface should be quick and intuitive to learn, but it is always going to depend on the complexity and specialisation of the system. Something such as an information kiosk has to have a zero learning curve, whereas the interface for a complex piece of 3D animation software is always going to take a while to learn (and trying to make such a piece of software easy to learn would inevitably compromise its features and power).
   
• Consistency
  Consistency is more important than anything else in interface design. It ties everything all the components of an interface together. It is fairly easy to achieve in terms of the visual design and icon design, but a lot of designers fail when it comes to the layout of different screens, dialogue boxes and that kind of thing. Maintaining commonality, (visually and structurally), between all your different interface elements is extremely important.
   
• Intuitiveness
  What makes an interface intuitive? It's easy to define, but very hard to put into action, and many interface designers struggle here. One problem is that of perspective - when you've been looking at an interface in development for a long time, it's very hard to see how a new user will interpret it.
  
  Nevertheless, like learnability, intuitiveness is extremely important in interface design. It's not the same as just making it easy to use, but rather designing the interface so that it feels like second nature to use.
   
• Prevention
  It's better to stop a user from doing something unwanted before they do it, rather than telling them off afterwards (kind of like with fighting crime - something that most governments don't seem to get!).
  
  The simple way to do this is usually by greying out buttons or menu items as appropriate, but there are other methods.
   
• Metaphors and idioms
  Metaphors and idioms are ubiquitous in interface design. Metaphors suggest an idea or some functionality to the user by way of a simple graphic device, usually an icon (for example, the metaphor of a disk in an icon represents 'save' functionality). Applications are also often encompassed in a global metaphor, such as the idea of a desktop.
  
  Idioms are commonplace interface elements that most users will instantly recognise and know how to use - scrollbars, for example.
   
• Simplicity
  The simplest ideas are often the best, and interface design is no exception. Simplicity is important here as it can help to keep your system intuitive and easily learn-able.
  
  That goes for the look of your interface (keeping things clutter-free), the work-flows involved (keeping the number of dialogues and clicks required to complete a task to the minimum) and your feature set (not overwhelming a user with too many features and options).
  
  But - always remember, there is a big different between simple and simplistic. Simple means refined and carefully considered, simplistic merely bodged together without much thought.
  
   
• Aesthetics
  Last, but, of course, not least, the aesthetics are extremely important. It doesn't matter how well executed an interface is, or how easy it is to learn and use, if it's ugly, most people will be turned off by it. Some types applications are almost always well designed from this point of view, but many are just left plain ugly, on the basis that, "that's how things are done in this industry," or, worse, "that's how our types of users like it."
  
  This is a huge failing. Note that an aesthetically pleasing interface doesn't imply anything fancy, distracting or flashy. Something a> can also be incredibly aesthetic.
  
  Icons can often make or break the aesthetic appeal of a web site or software interface, especially when your windows and dialogue box styles are limited by the operating system. Indeed, Steve Jobs himself has stated that the most important difference between Windows and Mac OSX is that Apple, to quote, "make the icons so good you'll want to lick them."

Usability

• Who will be using the interface and what knowledge do they already possess?
   
• What would the users of the interface like to be able to do?
   
• What, if anything, will the application need to be able to do without user guidance?
   
• What context will the user be working under? Are they in a high pressure environment or working from home?
   
• What kind of errors will users be making and how often will they be making them?
   
• How fast will users need to complete their tasks? Air traffic controllers need to be able to work quickly compared to, say, a writer or journalist.
   
• How much training will users require or be able to have in order to use the system? Detailed accounting software will obviously have a different learning curve than an information kiosk at a museum.
   
• What are the expectations or limitations of your target demographic of users?
  A highly trained engineer might well have different expectations of a piece of architectural software than someone who just wants to do some quick visualisations.