Design involves finding solutions that fit the user, task, and context of use. Properly designed objects -- including software, tools, and web sites -- fit their context so well that they are easy to use and beneficial to the user.

Design is:

• A discipline that explores the dialogue between products, people, and contexts.
• A process that defines a solution to help people achieve their goals.
• An artifact produced as the result of solution definition.

Design as a Discipline

Design is a discipline with a long history and many branches or areas of specialty. The usability profession is primarily concerned with Interaction Design (IxD), a newer branch of design dedicated to defining the behavior of digital products and systems. More traditional branches of design include Industrial Design (ID), which focuses on optimizing the function, value and appearance of physical objects, and Graphic Design (GD), which has strong roots in graphic arts and print media, and focuses on bringing together the meaning and appearance of a product. All branches of design involve innovating a new "form" or object that fits well into the context in which it will be used (Alexander, 1970).

Design as a Process

There are established processes for interaction design in the context of a User-Centered Design (UCD) methodology. Designers must balance a variety of considerations, including the needs and goals of the users, the constraints imposed by the context of use, and the challenges that arise naturally from the interaction between humans and machines; to come up with solutions. Commonly used design methods include paper prototyping and cognitive walkthroughs. The design process is "iterative" meaning that proposed solutions are refined through repeated cycles of prototype evaluation.

Design can occur on several different levels, which build on one another (Garrett, 2002). At a minimum, we can distinguish:

• Conceptual design is a basic foundation that defines the structure of the solution, including the functional elements of the product, their relationships and the system behavior. Conceptual design is the vital stage of the product creation that defines the success or failure of the product usability.
• Physical design is a more refined level that defines the aesthetics of the solution. This includes, for example language (and, to some extent, content) and branding. In contrast with conceptual design, physical design defines the success or failure of the product appeal.

Design as an Artifact

The design process results in producing design artifacts that feed the consequent stages of product development. Design artifacts include various system models, design specifications, style guides, and prototypes, including low-fidelity prototypes, such as sketches and wireframes, and high-fidelity prototypes, such as mockups and system demos.

Achieving Usability Through Interaction Design

Good, usable products never happen by chance. Rather, they are achieved through design that is based on an understanding of the natural physical, psychological, and emotional characteristics of human beings, their tasks and work environment; the constraints of the technology; and creating an interactive experience that best "fits" the context and enables the human users to be successful.

Well designed products are easier to use (and/or learn to use) and are more beneficial to the user than poorly designed ones. Good design can increase productivity, satisfaction, and user acceptance. Good design can also focus limited resources towards building products which satisfy the goals of the user and away from products and features which do not (Cooper, 1999). Finally, design can impact commercial success: a usable design can be a decisive factor in a competitive marketplace.