A software design document outlines the specifications for software to provide a roadmap for developers. It is produced early in the process of developing software and may be modified in response to changing circumstances and needs. This documentation is designed for internal use and is usually not circulated outside the design team and the offices of the client. In some cases, excerpts may be published as part of research or communications with people outside the company.
Components of the software design document outline what the product is supposed to do and how it is supposed to do it. This includes the underlying architecture of the program along with all the features the developers need to include in the finished product. Documentation can discuss the graphical interface, and how users will interact with the program, in order to offer guidance to programmers as it moves through the phases of development.
Multiple personnel can be involved in the creation of a software design document. They discuss various needs and concerns to make sure the document is complete and confirm it accurately represents the needs of the clients. Their goal is to create a single uniform guide for members of the team to use. This ensures consistency in the development process, because everyone is using the same reference document when they design and implement features.
In addition to discussing how the software should perform, the software design document can explicitly cover the target audience. A company working on software controls for a piece of scientific equipment, for example, may assume that any user is a scientist or technician familiar with the machine. This means the software doesn’t need to include simplifications of technical language or discussions of what controls do, because the user should already know this.
By contrast, software designed for word processing may need documentation and a guide for users who aren’t as familiar with word processing and computers. It may be usable out of the box for someone with experience, but could have modules for people to use if they want to learn about features, get tutorials, or seek help with a specific task. The parameters set out in a software design document for more technical projects may recommend leaving out some documentation and user guidance on the argument that users of the software don’t need this, which means there may be no reason to invest time and energy in developing it.