A design specification is a thorough document that contains a list of details about a product or process. For instance, the design specification might contain required dimensions, environmental factors, ergonomic aspects, aesthetic elements, required maintenance, and so on. The design specification serves as a guide for those who will implement the design. It allows these individuals to understand exactly what they are working with both functionally and aesthetically. The design brief is a short document (one or two pages) that describes the project within which the design is to be implemented. This description should include: whom the design is for (i.e., users), what their needs or requirements are, any limitations or constraints related to time, money, or other factors, and so forth. Often, the design brief is used as input to the design process by providing the developer with a clear picture of the project's goals and objectives. In addition to these documents, many designers create models, photographs, sketches, and other documentation tools that help them better understand their clients' needs and provide a means by which these can be translated into functional designs. These documents are important components in the design process because without them there would be no way to communicate effectively with others about the design vision, no way to ensure consistency between various parts of the project, and no way to avoid duplicating work effort.