From Just Solve the File Format Problem
SDA (StarOffice Draw, StarDraw) is the native vector graphics format of the StarOffice office suite, version 5.x and earlier. It is the predecessor of SXD. Refer to StarOffice binary formats for more information.
StarOffice StarDraw is not to be confused with the unrelated software from Stardraw.com (see Wikipedia:StarDraw).
There is contradictory information about the Draw file extension used by StarOffice versions 3 and 4. Some sources say it is .sdd, even though that conflicts with StarOffice Impress. Others say it is .sda, which seems more plausible.