This system allows both the source code and the documentation for the source to exist in the same file. This close proximity will increase the chances that the reference document will remain up to date. This allows much of the reference document to be generated automatically from the source code. The first revision of this system used a language similar to the roff dialects. This language was abandoned in favor of SGML , Standard Generalized Markup Language.
Generalized markup is a better model for information reuse and flexibility.
It allows the information it structures to be used by a variety of applications. SGML provides a good basis for future expansion. Many successful applications already use SGML , and the work they and the various standardization groups have done can be leveraged to our benefit. The motivation for generalized markup is a departure from that of traditional markup languages. With traditional markup languages, the goal is to add additional information to a document to allow it to be formatted for presentation.