A Document Type Definition (DTD) is a set of markup declarations that define a document type for an SGML-family markup language (SGML, XML, HTML).
A DTD uses a terse formal syntax that declares precisely which elements and references may appear where in the document of the particular type, and what the elements’ contents and attributes are. A DTD can also declare entities which may be used in the instance document.
XML uses a subset of SGML DTD.
As of 2009 newer XML namespace-aware schema languages (such as W3C XML Schema and ISO RELAX NG) have largely superseded DTDs. A namespace-aware version of DTDs is being developed as Part 9 of ISO DSDL. DTDs persist in applications which need special publishing characters such as the XML and HTML Character Entity References, which were derived from the larger sets defined as part of the ISO SGML standard effort.
Read more about Document Type Definition: Associating DTDs With Documents, Markup Declarations, XML DTDs and Schema Validation, XML DTD Schema Example
Famous quotes containing the words document, type and/or definition:
“... research is never completed ... Around the corner lurks another possibility of interview, another book to read, a courthouse to explore, a document to verify.”
—Catherine Drinker Bowen (1897–1973)
“I can barely conceive of a type of beauty in which there is no Melancholy.”
—Charles Baudelaire (1821–1867)
“The physicians say, they are not materialists; but they are:MSpirit is matter reduced to an extreme thinness: O so thin!—But the definition of spiritual should be, that which is its own evidence. What notions do they attach to love! what to religion! One would not willingly pronounce these words in their hearing, and give them the occasion to profane them.”
—Ralph Waldo Emerson (1803–1882)