Standard Generalized Markup Language
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| Standard Generalized Markup Language | |
|---|---|
 A fragment of the Oxford English Dictionary (1985), showing SGML markup |
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| File extension: | none |
| MIME type: | text/sgml |
| Uniform Type Identifier: | public.xml |
| Type of format: | metalanguage |
| Extended from: | GML |
| Extended to: | HTML, XML |
| Standard(s): | ISO 8879 |
The Standard Generalized Markup Language (SGML) is a metalanguage in which one can define markup languages for documents. SGML is a descendant of IBM's Generalized Markup Language (GML), developed in the 1960s by Charles Goldfarb, Edward Mosher and Raymond Lorie (whose surname initials were used by Goldfarb to make up the term GML). SGML and GML should not be confused with the Game Maker scripting language, or with the Geography Markup Language developed by the Open GIS Consortium.
SGML provides a variety of markup syntaxes that can be used for many applications. By changing the SGML Declaration one does not even need to use "angle brackets" although they are the norm, the so-called concrete reference syntax.
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[edit] Original uses
SGML was originally designed to enable the sharing of machine-readable documents in large projects in government, legal and the aerospace industry, which have to remain readable for several decades—a very long time in information technology. It has also been used extensively in the printing and publishing industries, but its complexity has prevented its widespread application for small-scale general-purpose use. Primarily intended for text and database publishing, one of its first major applications was the second edition of the Oxford English Dictionary, which was and is wholly marked up in SGML.
[edit] Syntax
SGML syntax example:
<QUOTE TYPE="example"> typically something like <ITALICS>this</ITALICS> </QUOTE>
SGML is an ISO standard. The standard it must conform to is: "ISO 8879:1986 Information processing—Text and office systems—Standard Generalized Markup Language (SGML)" which was accepted as a recognized standard in October of 1986.
[edit] Derivatives
[edit] HTML
HTML was originally designed based on SGML tagging but without SGML's emphasis on rigorous markup. It was later reformulated (at version 2.0) to be an application of SGML, although there's some debate on whether it ever actually became one.
[edit] XML
XML is derived from SGML and covers a broad spread of applications. XML is a profile—a specific subset of SGML, designed to be simpler to parse and process than full SGML, and to have more lightweight internationalization. XML is a simplification of SGML for general-purpose applications, such as the Semantic Web. XML has been used for a large number of applications, including notably XHTML, RSS, Atom, XML-RPC and SOAP.
[edit] Docbook
Another markup language originally created as an application of SGML is DocBook, designed for authoring technical documentation. DocBook is now also available as an XML application.
[edit] Other
There are also a number of languages that are related in part to SGML and XML, but, because they cannot be parsed or validated or otherwise processed using standard SGML and XML tools, cannot be considered to be applications of SGML or XML. One example is the Z Format, a language designed for typesetting and documentation.
