Standard Generalized Markup Language
(SGML) A generic markup language for representing documents. SGML is an International Standard that describes the relationship between a document's content and its structure. SGML allows document-based information to be shared and re-used across applications and computer platforms in an open, vendor-neutral format. SGML is sometimes compared to SQL, in that it enables companies to structure information in documents in an open fashion, so that it can be accessed or re-used by any SGML-aware application across multiple platforms.
SGML is defined in "ISO 8879:1986 Information processing -- Text and office systems -- Standard Generalized Markup Language (SGML)", an ISO standard produced by JTC 1/SC 18 and amended by "Amendment 1:1988".
Unlike other common document file formats that represent both content and presentation, SGML represents a document's content data and structure (interrelationships among the data). Removing the presentation from content establishes a neutral format. SGML documents and the information in them can easily be re-used by publishing and non-publishing applications.
SGML identifies document elements such as titles, paragraphs, tables, and chapters as distinct objects, allowing users to define the relationships between the objects for structuring data in documents. The relationships between document elements are defined in a Document Type Definition (DTD). This is roughly analogous to a collection of field definitions in a database. Once a document is converted into SGML and the information has been 'tagged', it becomes a database-like document. It can be searched, printed or even programmatically manipulated by SGML-aware applications.
Companies are moving their documents into SGML for several reasons:
Interchange - SGML is a core data standard that enables SGML-aware applications to inter-operate and share data seamlessly.
A central SGML document store can feed multiple processes in a company, so managing and updating information is greatly simplified. For example, when an aeroplane is delivered to a customer, it comes with thousands of pages of documentation. Distributing these on paper is expensive, so companies are investigating publishing on CD-ROM. If a maintenance person needs a guide for adjusting a plane's flight surfaces, a viewing tool automatically assembles the relevant information from the document repository as a complete document. SGML can be used to define attributes to information stored in documents such as security levels.
Electronic Delivery is widely regarded as the most compelling reason companies are moving to SGML. Electronic delivery enables users to retrieve information on-line using an intelligent document viewer.
See also sgmls.
["The SGML Handbook", Charles F. Goldfarb, Clarendon Press, 1991, ISBN 0198537379. (Full text of the ISO standard plus extensive commentary and cross-referencing. Somewhat cheaper than the ISO document)].
[Example of some SGML?]