SGMLfamily

SGMLfamily refers to the set of markup languages that are defined by, or derive from, the Standard Generalized Markup Language (SGML). It is not a formal standard, but a descriptive umbrella used in documentation and discussion to describe SGML-based ecosystems, including SGML, XML, and XML-derived languages, as well as various SGML-inspired publishing languages such as DocBook and TEI.

SGML, specified by ISO 8879 (1986), introduced the concepts of a document type definition (DTD), elements, attributes, entities, and a robust parsing model. XML, developed by the W3C starting in 1996, retains the basic SGML heritage but emphasizes simplicity and well-formedness, with a more constrained DTD or XML Schema for validation, namespaces, and Unicode. The SGMLfamily is thus defined by a shared lineage and common ideas about structure, validation, and portable interchange.

Common members include SGML itself, XML (and XML-based languages such as XHTML), and document grammars used in publishing like DocBook, TEI, and TEI-lite with XML or SGML serializations. HTML is related as a practical offshoot derived from SGML concepts rather than a strict SGML instance; XHTML is a strict XML serialization of HTML.

Impact and usage: The SGMLfamily has been central to large-scale documentation, data interchange, and digital libraries. While XML has largely supplanted SGML for new projects due to its simpler model, SGML remains in use in legacy systems and in contexts requiring the full SGML feature set. Tools include grammar-driven parsers, validators, and editors that support DTDs and schemas.