Describes: (a) an abstract syntax known as the Standard Generalized Markup Language (SGML). Also specifies language expresses the description of a document's structure and other attributes, as well as other information that makes the markup interpretable; (b) a reference concrete syntax that binds the abstract syntax to specific characters and numeric values, and criteria for defining variant concrete syntaxes; (c) conforming documents in terms of their use of components of the language; (d) conforming systems in terms of their ability to process conforming documents and to recognize markup errors in them; and (e) how data not defined by this International Standard (such as images, graphics, or formatted text) can be included in a conforming document.

ISO 8879 : 1986(R2008) - Identical