This is the part 2 of 4.

Some times an application, or its user interface, seem to exist more for themselves rather than around the purpose of being a tool to accomplish a task: it’s very important that always stays the first goal of the existence of any functionality the software offers, being an application, a particular screen of that application, or a piece of the shell.

• The star of the user interface is the content, this has to always remain the center, what distracts from the content is something that is often not necessary and can be avoided.
• You interact with objects represented on the screen with a particular input system, may be a mouse, a trackpad or the touch screen. Interaction should be direct: in the real world you interact with an object not with a remote control that remote controls the object. Objects represented on the screen are often quite abstract, from objects to “pure information”, so is not always easy avoiding levels of indirection, but they should be limited (one of the reasons you will see handles in Plasma and not things like text boxes that ask how many pixels you want your panel high).
• Our mind is trained to recognize patterns, that’s why consistency in UI is extremely important: this is something that comes from our evolution: for our survival we have to memorize and then recognize anything new that we encounter, may be a menace or an opportunity. Once you learn what a snake is, when you see a very different type of snake you just run;). Same thing as learning to use a tool, and transferring this knowledge to the use of different and perhaps more advanced tools, and this is what interest us here. (see transfer of learning)
• Organic user interfaces: same reason as the above point, our mind expect things that we have seen the past some million years: some things are hardwired in our brains: we expect that when something appears it comes moving from somewhere. Something appearing out of the blue without having being noticed it was coming it’s seen as a potential menace, if you just find yourself with a big spider in front of you all the sudden without having it seen coning from somewhere, is possibly even more terrifying.
  As important as UI element coming in from somewhere is “natural” shapes: even just using rounded corners when possible instead of perfect edges may do quite a lot of difference. There are two probable reasons here: a shape with sharp edges focuses the attention on the outside of the shape, where the edges are pointing, while a shape with rounded corners focuses the attention inside the shape. Moreover, in nature things with sharp edges again are a menace.
• Finally, a good interface should be invisible. What? Again, the sole purpose of the interface is being a tool designed to do a particular task. Everything that is “more” that the strict use case of the particular UI hinders its learnability and efficience. Often most of an application UI can be seen as “Content”, “Document” that still is a UI artefact, but is a quite direct representation of what you are viewing or working on, with chrome as everything else, that is often necessary, maybe a necessary evil, but evil still.

Those are all concepts that gained quite a lot of traction over the last few years, and UI quality all around, from Windows to KDE to web apps improved a lot, most applications and environments we see around followed a very clear design procedure, but… there is a but 😉

There is also an ugly side about it.. in the next post.