This is a recommended practice for describing software designs. It specifies the necessary information content, and recommended organization for a software design description. A software design description is a representation of a software system that is used as a medium for communicating software design information. The practice may be applied to commercial, scientific, or military software that runs on any digital computer. Applicability is not restricted by the size, complexity, or criticality of the software. This practice is not limited to specific methodologies for design, configuration management, or quality assurance. It is assumed that the quality design information and changes to the design of description will be managed by other project activities. Finally, this document does not support nor is it limited to any particular descriptive technique. It maybe applied to paper documents, automated databases, design description languages, or other means of description.