4.1. Formal definition#
A design is a concept of either an object, a process, or a system that is specific and, in most cases, detailed. Design refers to something that is or has been intentionally created by a thinking agent, though it is sometimes used to refer to the nature of something. The verb to design expresses the process of developing a design. In some cases, the direct construction of an object without an explicit prior plan may also be considered to be a design (such as in some artwork and craftwork). The design usually has to satisfy certain goals and constraints; may take into account aesthetic, functional, economic, or socio-political considerations; and is expected to interact with a certain environment. - Wikipedia
The following formal definition of engineering design is the most useful one for the purpose of this ebook [6, p.7]:
Engineering design is a systematic, intelligent process in which engineers generate, evaluate, and specify solutions for devices, systems, or processes whose form(s) and function(s) achieve clients’ objectives and users’ needs while satisfying a specified set of constraints. In other words, engineering design is a thoughtful process for generating plans or schemes for devices, systems, or processes that attain given objectives while adhering to specified constraints.
It is important to recognize that when we are designing devices, systems, and processes, we are designing artifacts: artificial, man made objects, the “things” or devices that are being designed. They are most often physical object such as airplanes, wheelchairs, ladders, cell hones, and carburetors. But “paper” products (or their electronic versions) such as drawings, plans, computer software, articles, and books are also artifacts in this sense. In this book we will use device, artifact, or system rather interchangeably as the object of our design.
With further recourse to our ‘design dictionary’, we note the following definitions:
Design objective: a feature or behavior that we wish the design to have or exhibit.
Design constraint: a limit or restriction on the features or behaviors of the design. A proposed design is unacceptable if these limits are violated.
Functions: things a designed device or system is supposed to do. Engineering functions almost always involve transforming or transferring energy, information, or material. We view energy transformation or transfer quite broadly; It includes supporting and transmitting forces, the flow of current, the flow of charge, the transfer of material, and so on.
Means: a way or a method to make a function happen. For example, friction is a means for fulfilling a function of applying a braking force.
Form: the shape and structure of something as distinguished from its material We will not deal with form very much in this book, but form is central to industrial design, a very important part of product design.
Note that objectives for a design are different from the constraints placed on a design. Objectives may be completely or partially achieved, or may not be achieved at all. Constraints, on the other hand, must be satisfied or the design is not acceptable.