A software design document is a written description of a software product, that a software designer writes in order to give a software development team an overall guidance of the architecture of the software project. A software design document usually accompanies an architecture diagram with pointers to detailed feature specifications of smaller pieces of the design. A design document needs to be a stable reference, outlining all parts of the software and how they will work. The document is commanded to give a fairly complete description, while maintaining a high-level view of the software.
The following Design Documents are available here for GMAT:
The architecture design uses information flowing characteristics, and maps them into the program structure. The transformation mapping method is applied to exhibit distinct boundaries between incoming and outgoing data. The data flow diagrams allocate control input, processing and output along three separate modules.
The interface specs are working documents that describe all GMAT features at the user interface and functional level. These documents contain high level working requirements, feature overview, details of the GUI and script interfaces, and detailed descriptions of how each feature works.
The detailed design specs provide information about the software design for specific features of the system. These pages contain class diagrams and other UML based artifacts that define how specific parts of GMAT work.