- Standard Generalized Markup Language: the international standard
for structured document interchange, ISO 8879 (1986)
- Developed out of a search for a universal typesetting language
begun in the late 1960s
- Descriptive, not procedural -- the procedures are left to
formatting/presentation systems
- Not a single markup language, but a metalanguage for the
specification of an unlimited number of markup languages, each
optimized for a particular category of documents
- The SGML description of a markup language is called a Document
Type Definition (DTD)
- In SGML, the DTD is a required part of the document