Editing Markup language (section)

==History of markup languages<span class="anchor" id="History"></span>==
===GenCode===
The first well-known public presentation of markup languages in computer text processing was made by [[William W. Tunnicliffe]] at a conference in 1967, although he preferred to call it ''generic coding.'' It can be seen as a response to the emergence of programs such as [[RUNOFF]] that each used their own control notations, often specific to the target typesetting device. In the 1970s, Tunnicliffe led the development of a standard called GenCode for the publishing industry and later was the first chairman of the [[International Organization for Standardization]] committee that created [[SGML]], the first standard descriptive markup language. [[Book design|Book designer]] Stanley Rice published speculation along similar lines in 1970.<ref>Rice, Stanley. “Editorial Text Structures (with some relations to information structures and format controls in computerized composition).” American National Standards Institute, March 17, 1970.</ref>

[[Brian Reid (computer scientist)|Brian Reid]], in his 1980 dissertation at [[Carnegie Mellon University]], developed the theory and a working implementation of descriptive markup in actual use. However, [[IBM]] researcher [[Charles Goldfarb]] is more commonly seen today as the "father" of markup languages. Goldfarb hit upon the basic idea while working on a primitive document management system intended for law firms in 1969, and helped invent [[IBM Generalized Markup Language|IBM GML]] later that same year. GML was first publicly disclosed in 1973.

In 1975, Goldfarb moved from [[Cambridge, Massachusetts]] to [[Silicon Valley]] and became a product planner at the [[IBM Almaden Research Center]]. There, he convinced IBM's executives to deploy GML commercially in 1978 as part of IBM's Document Composition Facility product, and it was widely used in business within a few years.

SGML, which was based on both GML and GenCode, was an [[International Organization for Standardization|ISO]] project worked on by Goldfarb beginning in 1974.<ref>{{cite web|url=http://www.drdobbs.com/blog/archives/2009/08/beyond_html_an.html|title=2009 interview with SGML creator Charles F. Goldfarb|publisher=[[Dr. Dobb's Journal]]|access-date=2010-07-18}}{{dead link|date=January 2018 |bot=InternetArchiveBot |fix-attempted=yes }}</ref> Goldfarb eventually became chair of the SGML committee. SGML was first released by ISO as the ISO 8879 standard in October 1986.

===troff and nroff===
{{Main|troff}}
Some early examples of computer markup languages available outside the publishing industry can be found in typesetting tools on [[Unix]] systems such as [[troff]] and [[nroff]]. In these systems, formatting commands were inserted into the document text so that typesetting software could format the text according to the editor's specifications. It was a [[trial and error]] iterative process to get a document printed correctly.<ref>Daniel Gilly. [http://web.deu.edu.tr/doc/oreily/unix/unixnut/ch12_01.htm ''Unix in a nutshell: Chapter 12. Groff and Troff''] {{Webarchive|url=https://web.archive.org/web/20160105180006/http://web.deu.edu.tr/doc/oreily/unix/unixnut/ch12_01.htm |date=2016-01-05 }}. O'Reilly Books, 1992. {{ISBN|1-56592-001-5}}</ref> Availability of [[WYSIWYG]] ("what you see is what you get") publishing software supplanted much use of these languages among casual users, though serious publishing work still uses markup to specify the non-visual structure of texts, and WYSIWYG editors now usually save documents in a markup-language-based format.

===TeX===
{{Main|TeX}}
Another major publishing standard is [[TeX]], created and refined by [[Donald Knuth]] in the 1970s and '80s. [[TeX]] concentrated on the detailed layout of text and font descriptions to typeset mathematical books. This required Knuth to spend considerable time investigating the art of [[typesetting]]. TeX is mainly used in [[academia]], where it is a [[De facto standard|''de facto'' standard]] in many scientific disciplines. A TeX macro package known as [[LaTeX]] provides a descriptive markup system on top of TeX, and is widely used both among the scientific community and the publishing industry.

===Scribe, GML, and SGML===
{{Main|Scribe (markup language)|IBM Generalized Markup Language|Standard Generalized Markup Language}}
The first language to make a clean distinction between structure and presentation was [[Scribe (markup language)|Scribe]], developed by [[Brian Reid (computer scientist)|Brian Reid]] and described in his doctoral thesis in 1980.<ref>Reid, Brian. "Scribe: A Document Specification Language and its Compiler". Ph.D. thesis, Carnegie-Mellon University, Pittsburgh PA. Also available as Technical Report CMU-CS-81-100.</ref> Scribe was revolutionary in a number of ways, introducing the idea of styles separated from the marked-up document, and a [[grammar]] that controlled the usage of descriptive elements. Scribe influenced the development of [[IBM Generalized Markup Language|Generalized Markup Language]] (later SGML),<ref>{{Cite web|url=http://xml.coverpages.org/mt98-papers.html#reid|title=20 Years of Abstract Markup - Any Progress?|last=Reid|first=Brian|author-link=Brian Reid (computer scientist)|website=xml.coverpages.org|access-date=2021-08-16|archive-date=2019-05-01|archive-url=https://web.archive.org/web/20190501150514/http://xml.coverpages.org/mt98-papers.html#reid|url-status=live}}</ref> and is a direct ancestor to [[HTML]] and [[LaTeX]].<ref>HTML is a particular instance of SGML, whereas LaTeX is designed with the separation-between-content-and-design philosophy of Scribe in mind.</ref>

In the early 1980s, the idea that markup should focus on the structural aspects of a document and leave the visual presentation of that structure to the interpreter led to the creation of [[Standard Generalized Markup Language|SGML]]. The language was developed by a committee chaired by Goldfarb. It incorporated ideas from many different sources, including Tunnicliffe's project, GenCode. Sharon Adler, Anders Berglund, and James A. Marke were also key members of the SGML committee.

SGML specified a syntax for including the markup in documents, as well as one for separately describing ''what'' tags were allowed, and ''where'' (the Document Type Definition ([[Document Type Definition|DTD]]), later known as a [[XML schema|schema]]). This allowed authors to create and use any markup they wished, selecting tags that made the most sense to them and were named in their own natural languages, while also allowing automated verification. Thus, SGML is properly a [[metalanguage]], and many particular markup languages are derived from it. From the late '80s onward, most substantial new markup languages have been based on the SGML system, including for example [[Text Encoding Initiative|TEI]] and [[DocBook]]. SGML was promulgated as an International Standard by [[International Organization for Standardization]], ISO 8879, in 1986.<ref>{{Cite web|url=https://www.iso.org/standard/16387.html|title=ISO 8879:1986|website=ISO|access-date=2021-08-15|archive-date=2021-08-17|archive-url=https://web.archive.org/web/20210817024719/https://www.iso.org/standard/16387.html|url-status=live}}</ref>

SGML found wide acceptance and use in fields with very large-scale documentation requirements. However, many found it cumbersome and difficult to learn — a side effect of its design attempting to do too much and being too flexible. For example, SGML made end tags (or start-tags, or even both) optional in certain contexts, because its developers thought markup would be done manually by overworked support staff who would appreciate saving keystrokes{{Citation needed|date=August 2008}}.

====HTML====
{{Main|HTML}}
In 1989, computer scientist [[Tim Berners-Lee|Sir Tim Berners-Lee]] wrote a memo proposing an [[Internet]]-based [[hypertext]] system,<ref>Tim Berners-Lee, "[https://www.w3.org/History/1989/proposal.html Information Management: A Proposal]". CERN (March 1989, May 1990). W3C. {{Webarchive|url=https://web.archive.org/web/20100401051011/https://www.w3.org/History/1989/proposal.html |date=2010-04-01 }}</ref> then specified HTML and wrote the browser and server software in the last part of 1990. The first publicly available description of HTML was a document called "HTML Tags", first mentioned on the Internet by Berners-Lee in late 1991.<ref name="tagshtml">{{cite web |url=https://www.w3.org/History/19921103-hypertext/hypertext/WWW/MarkUp/Tags.html |title=Tags used in HTML |publisher=World Wide Web Consortium |date=November 3, 1992 |access-date=2021-08-16 |archive-date=2010-01-31 |archive-url=https://web.archive.org/web/20100131184344/http://www.w3.org/History/19921103-hypertext/hypertext/WWW/MarkUp/Tags.html |url-status=live }}</ref><ref>{{cite web|url=https://lists.w3.org/Archives/Public/www-talk/1991SepOct/0003.html|title=First mention of HTML Tags on the www-talk mailing list|publisher=World Wide Web Consortium|date=October 29, 1991|access-date=August 16, 2021|archive-date=August 8, 2021|archive-url=https://web.archive.org/web/20210808223716/https://lists.w3.org/Archives/Public/www-talk/1991SepOct/0003.html|url-status=live}}</ref> It describes 18 elements comprising the initial, relatively simple design of HTML. Except for the hyperlink tag, these were strongly influenced by [[SGMLguid]], an in-house [[SGML]]-based documentation format at [[CERN]], and very similar to the sample schema in the SGML standard. Eleven of these elements still exist in HTML 4.<ref>{{cite web|url=https://www.w3.org/TR/1999/REC-html401-19991224/index/elements|title=Index of elements in HTML 4|publisher=World Wide Web Consortium|date=December 24, 1999|access-date=2021-08-16|archive-date=2007-05-05|archive-url=https://web.archive.org/web/20070505172415/https://www.w3.org/TR/1999/REC-html401-19991224/index/elements|url-status=live}}</ref>

Berners-Lee considered HTML an SGML application. The [[Internet Engineering Task Force]] (IETF) formally defined it as such with the mid-1993 publication of the first proposal for an HTML specification: [https://www.w3.org/MarkUp/draft-ietf-iiir-html-01.txt "Hypertext Markup Language (HTML)" Internet-Draft] {{Webarchive|url=https://web.archive.org/web/20170103041713/https://www.w3.org/MarkUp/draft-ietf-iiir-html-01.txt |date=2017-01-03 }} by Berners-Lee and [[Dan Connolly (computer scientist)|Dan Connolly]], which included an SGML [[Document Type Definition]] to define the grammar.<ref>{{cite web|url=https://lists.w3.org/Archives/Public/www-talk/1991NovDec/0020.html|title=Re: SGML/HTML docs, X Browser (archived www-talk mailing list post)|author=Tim Berners-Lee|author-link=Tim Berners-Lee|date=December 9, 1991|quote=SGML is very general. HTML is a specific application of the SGML basic syntax applied to hypertext documents with a simple structure.|access-date=August 16, 2021|archive-date=July 3, 2021|archive-url=https://web.archive.org/web/20210703084047/https://lists.w3.org/Archives/Public/www-talk/1991NovDec/0020.html|url-status=live}}</ref> Many of the HTML text elements are found in the 1988 ISO technical report TR 9537 ''Techniques for using SGML'', which in turn covers the features of early text formatting languages such as that used by the [[TYPSET and RUNOFF|RUNOFF command]] developed in the early 1960s for the [[Compatible Time-Sharing System|CTSS]] (Compatible Time-Sharing System) operating system. These formatting commands were derived from those used by typesetters to manually format documents. [[Steven DeRose]]<ref>DeRose, Steven J. "The SGML FAQ Book". Boston: Kluwer Academic Publishers, 1997. {{ISBN|0-7923-9943-9}}</ref> argues that HTML's use of descriptive markup (and the influence of SGML in particular) was a major factor in the success of the Web, because of the flexibility and extensibility that it enabled. HTML became the main markup language for creating web pages and other information that can be displayed in a web browser and is likely the most used markup language in the world today.

===XML===
{{Main|XML}}

XML (Extensible Markup Language) is a meta markup language that is very widely used. XML was developed by the [[World Wide Web Consortium]] in a committee created and chaired by [[Jon Bosak]]. The main purpose of XML was to simplify SGML by focusing on a particular problem — documents on the Internet.<ref>{{cite web |url=https://www.w3.org/TR/xml11/ |date=16 August 2006 |title=Extensible Markup Language (XML) 1.1 (Second Edition) |publisher=W3C |access-date=2021-08-16 |archive-date=2021-08-11 |archive-url=https://web.archive.org/web/20210811223058/https://www.w3.org/TR/xml11/ |url-status=live }}</ref> XML remains a metalanguage like SGML, allowing users to create any tags needed (hence "extensible") and then describing those tags and their permitted uses.

XML adoption was helped because every XML document can be written in such a way that it is also an SGML document, and existing SGML users and software could switch to XML fairly easily. However, XML eliminated many of the more complex features of SGML to simplify implementation environments such as documents and publications. It appeared to strike a happy medium between simplicity and flexibility, as well as supporting very robust schema definition and validation tools, and was rapidly adopted for many other uses. XML is now widely used for communicating [[database transaction|data]] between applications, for serializing program data, for hardware communications protocols, vector graphics, and many other uses as well as documents.

====XHTML====
{{Main|XHTML}}
From January 2000 until HTML 5 was released, all [[W3C Recommendation]]s for HTML have been based on XML, using the abbreviation [[XHTML]] ('''Ex'''tensible '''H'''yper'''T'''ext '''M'''arkup '''L'''anguage). The language specification requires that XHTML Web documents be ''well-formed'' XML documents. This allows for more rigorous and robust documents, by avoiding many syntax errors which historically led to incompatible browser behaviors, while still using document components that are familiar with HTML.

One of the most noticeable differences between HTML and XHTML is the rule that ''all tags must be closed'': empty HTML tags such as <code><nowiki><br></nowiki></code> must either be ''closed'' with a regular end-tag, or replaced by a special form: {{nowrap|<code><nowiki><br /></nowiki></code>}} (the space before the '<code><nowiki>/</nowiki></code>' on the end tag is optional, but frequently used because it enables some pre-XML Web browsers, and SGML parsers, to accept the tag). Another difference is that all [[HTML#Attributes|attribute]] values in tags must be quoted. Both these differences are commonly criticized as verbose but also praised because they make it far easier to detect, localize, and repair errors. Finally, all tag and attribute names within the XHTML namespace must be lowercase to be valid. HTML, on the other hand, was case-insensitive.

====Other XML-based applications====
Many XML-based applications now exist, including the [[Resource Description Framework]] as [[RDF/XML]], [[XForms]], [[DocBook]], [[Simple Object Access Protocol|SOAP]], and the [[Web Ontology Language]] (OWL). For a partial list of these, see [[List of XML markup languages]].