The goal of user interface design is to make the user’s interaction as simple and efficient as possible, in terms of accomplishing user goals—what is often called user-centered design. Good user interface design facilitates finishing the task at hand without drawing unnecessary attention to itself. Graphic design may be utilized to support its usability. The design process must balance technical functionality and visual elements (e.g.,mental model) to create a system that is not only operational but also usable and adaptable to changing user needs.
Interface design is involved in a wide range of projects from computer systems, to cars, to commercial planes; all of these projects involve much of the same basic human interactions yet also require some unique skills and knowledge. As a result, designers tend to specialize in certain types of projects and have skills centered around their expertise, whether that be software design, user research, web design, or industrial design.
There are several phases and processes in the user interface design, some of which are more demanded upon than others, depending on the project. (Note: for the remainder of this section, the word system is used to denote any project whether it is a web site, application, or device.)
In rare cases, the graphics may drive the prototyping, depending on the importance of visual form versus function. If the interface requires multiple skins, there may be multiple interface designs for one control panel, functional feature or widget. This phase is often a collaborative effort between a graphic designer and a user interface designer, or handled by one who is proficient in both disciplines.
The dynamic characteristics of a system are described in terms of dialogue requirements contained in seven principles of part 10 of the ergonomics standard, the ISO 9241. This standard establishes a framework of ergonomic “principles” for the dialogue techniques with high-level definitions and illustrative applications and examples of the principles. The principles of the dialogue represent the dynamic aspects of the interface and can be mostly regarded as the “feel” of the interface.
The seven dialogue principles are:
The concept of usability is defined in Part 11 of the ISO 9241 standard by effectiveness, efficiency, and satisfaction of the user.
Part 11 gives the following definition of usability:
Effectiveness, efficiency, and satisfaction can be seen as quality factors of usability. To evaluate these factors, they need to be decomposed into sub-factors, and finally, into usability measures.
The information presentation is described in Part 12 of the ISO 9241 standard for the organization of information (arrangement, alignment, grouping, labels, location), for the display of graphical objects, and for the coding of information (abbreviation, color, size, shape, visual cues) by seven attributes. The “attributes of presented information” represent the static aspects of the interface and can be generally regarded as the “look” of the interface. The attributes are detailed in the recommendations given in the standard. Each of the recommendations supports one or more of the seven attributes.
The seven presentation attributes are:
The user guidance in Part 13 of the ISO 9241 standard describes that the user guidance information should be readily distinguishable from other displayed information and should be specific for the current context of use.
User guidance can be given by the following five means:
User interface design has been a topic of considerable research, including on its aesthetics.In the past standards have been developed, as far back as the eighties for defining the usability of software products.One of the structural basis has become the IFIP user interface reference model. The model proposes four dimensions to structure the user interface:
This model has greatly influenced the development of the international standard ISO 9241 describing the interface design requirements for usability. The desire to understand application-specific UI issues early in software development, even as an application was being developed, led to research on GUI rapid prototyping tools that might offer convincing simulations of how an actual application might behave in production use.Some of this research has shown that a wide variety of programming tasks for GUI-based software can, in fact, be specified through means other than writing program code.
Research in recent years is strongly motivated by the increasing variety of devices that can, by virtue of Moore’s Law, host very complex interfaces.
There is also research on generating user interfaces automatically, to match a user’s level of ability for different kinds of interaction.
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