A document type definition (DTD) is a specification file that contains set of markup declarations that define a document type for an SGML-family markup language. The DTD specification file can be used to validate documents.
HyperText Markup Language (HTML) is the standard markup language for documents designed to be displayed in a web browser. It defines the content and structure of web content. It is often assisted by technologies such as Cascading Style Sheets (CSS) and scripting languages such as JavaScript.
A markuplanguage is a text-encoding system which specifies the structure and formatting of a document and potentially the relationship between its parts. Markup can control the display of a document or enrich its content to facilitate automated processing.
The Standard Generalized Markup Language is a standard for defining generalized markup languages for documents. ISO 8879 Annex A.1 states that generalized markup is "based on two postulates":
Extensible Markup Language (XML) is a markup language and file format for storing, transmitting, and reconstructing arbitrary data. It defines a set of rules for encoding documents in a format that is both human-readable and machine-readable. The World Wide Web Consortium's XML 1.0 Specification of 1998 and several other related specifications—all of them free open standards—define XML.
The Document Style Semantics and Specification Language (DSSSL) is an international standard developed to provide stylesheets for SGML documents.
The Organization for the Advancement of Structured Information Standards is a nonprofit consortium that works on the development, convergence, and adoption of projects - both open standards and open source - for Computer security, blockchain, Internet of things (IoT), emergency management, cloud computing, legal data exchange, energy, content technologies, and other areas.
James Clark is a software engineer and creator of various open-source software including groff, expat and several XML specifications.
In web development, "tag soup" is a pejorative for HTML written for a web page that is syntactically or structurally incorrect. Web browsers have historically treated structural or syntax errors in HTML leniently, so there has been little pressure for web developers to follow published standards. Therefore there is a need for all browser implementations to provide mechanisms to cope with the appearance of "tag soup", accepting and correcting for invalid syntax and structure where possible.
A numeric character reference (NCR) is a common markup construct used in SGML and SGML-derived markup languages such as HTML and XML. It consists of a short sequence of characters that, in turn, represents a single character. Since WebSgml, XML and HTML 4, the code points of the Universal Character Set (UCS) of Unicode are used. NCRs are typically used in order to represent characters that are not directly encodable in a particular document. When the document is interpreted by a markup-aware reader, each NCR is treated as if it were the character it represents.
An XML schema is a description of a type of XML document, typically expressed in terms of constraints on the structure and content of documents of that type, above and beyond the basic syntactical constraints imposed by XML itself. These constraints are generally expressed using some combination of grammatical rules governing the order of elements, Boolean predicates that the content must satisfy, data types governing the content of elements and attributes, and more specialized rules such as uniqueness and referential integrity constraints.
The following tables compare general and technical information for a number of document markup languages. Please see the individual markup languages' articles for further information.
The term CDATA, meaning character data, is used for distinct, but related, purposes in the markup languages SGML and XML. The term indicates that a certain portion of the document is general character data, rather than non-character data or character data with a more specific, limited structure.
Data exchange is the process of taking data structured under a source schema and transforming it into a target schema, so that the target data is an accurate representation of the source data. Data exchange allows data to be shared between different computer programs.
A Formal Public Identifier (FPI) is a short piece of text with a particular structure that may be used to uniquely identify a product, specification or document. FPIs were introduced as part of Standard Generalized Markup Language (SGML), and serve particular purposes in formats historically derived from SGML. Some of their most common uses are as part of document type declarations (DOCTYPEs) and document type definitions (DTDs) in SGML, XML and historically HTML, but they are also used in the vCard and iCalendar file formats to identify the software product which generated the file.
Extensible HyperText Markup Language (XHTML) is part of the family of XML markup languages which mirrors or extends versions of the widely used HyperText Markup Language (HTML), the language in which Web pages are formulated.
A structured document is an electronic document where some method of markup is used to identify the whole and parts of the document as having various meanings beyond their formatting. For example, a structured document might identify a certain portion as a "chapter title" rather than as "Helvetica bold 24" or "indented Courier". Such portions in general are commonly called "components" or "elements" of a document.
An XML transformation language is a programming language designed specifically to transform an input XML document into an output document which satisfies some specific goal.
A document type declaration, or DOCTYPE, is an instruction that associates a particular XML or SGML document with a document type definition (DTD). In the serialized form of the document, it manifests as a short string of markup that conforms to a particular syntax.
