Reason 5: Design and Implementation Don't Always Match

The design of the user interface and the technical implementation of the user interface are different activities, requiring very different skills. Today, the emphasis and need are on design skills, while many engineers possess the mind-set and skill set for technical implementation.

Design, in this case, relates to how the product communicates, whereas implementation refers to how it works. Previously, this dichotomy between design and implementation was rarely even acknowledged. Engineers and designers were hired for their technical expertise (e.g., programming and machine-oriented analysis) rather than for their design expertise (e.g., communication and human-oriented analysis). This is understandable, because with early generation computer languages the great challenge lay in simply getting

the product to work. If it communicated elegantly as well, so much the better, but that was not the prime directive. 

With the advent of new-generation programming languages and tools to automatically develop program code, the challenge of technical implementation has diminished. The challenge of design, however, has increased dramatically due to the need to reach a broader, less sophisticated user population and the rising expectations for ease of use. To use a computer analogy, the focus has moved from the inside of the machine (how it works) to the outside where the end user resides (how it communicates).

What is needed are methods and techniques to help designers change the way they view and design products — methods that work from the outside in, from the end user's needs and abilities to the eventual implementation of the product is user-centered design (UCD). Because it is only within the context of UCD that usability testing makes sense and thrives, let's explore this notion of user-centered design in more detail