Standard Generalized Markup Language

Standard Generalized Markup Language (SGML) is a standard for how to specify a document markup language or tag set. It is a metadata markup language, meaning it is used to describe the structure and other attributes of a document rather than its content. SGML is a descendant of IBM's Generalized Markup Language (GML), developed in the 1960s by Charles Goldfarb, Edward Mosher and Raymond Lorie.

History

SGML was developed and standardized by the International Organization for Standardization (ISO) in 1986 as ISO 8879:1986. It was one of the first attempts to establish a universal standard for document markup, and has been influential in the development of other markup languages, such as HTML and XML.

Structure

SGML is based on elements, which are the basic units of structure in a document. Elements are defined by tags, which are text strings enclosed in angle brackets (< and >). Tags can be used to define a variety of elements, such as headings, paragraphs, lists, links, and more.

SGML also supports attributes, which provide additional information about an element. Attributes are included in the start tag of an element, and consist of a name and a value.

Applications

SGML has been used in a wide range of applications, from large technical documentation projects to electronic publishing. It is particularly well-suited to projects that require long-term document storage and retrieval, due to its flexibility and adaptability.

One of the most well-known applications of SGML is the DocBook document type, which is used for writing technical documentation. Other notable applications include the TEI (Text Encoding Initiative) guidelines for electronic text encoding and interchange, and the DARPA Agent Markup Language (DAML), used for semantic web services.

See also

• Document Type Definition
• HyTime
• XML Schema (W3C)