Markup language

In computer text processing, a markup language is a system for annotating a document in a way that is syntactically distinguishable from the text. The idea and terminology evolved from the 'marking up' of paper manuscripts (i.e., the revision instructions by editors), which is traditionally written with a red or blue pencil on authors' manuscripts. In digital media, this 'blue pencil instruction text' was replaced by tags, which indicate what the parts of the document are, rather than details of how they might be shown on some display. This lets authors avoid formatting every instance of the same kind of thing redundantly (and possibly inconsistently). It also avoids the specification of fonts and dimensions which may not apply to many users (such as those with varying-size displays, impaired vision and screen-reading software). In computer text processing, a markup language is a system for annotating a document in a way that is syntactically distinguishable from the text. The idea and terminology evolved from the 'marking up' of paper manuscripts (i.e., the revision instructions by editors), which is traditionally written with a red or blue pencil on authors' manuscripts. In digital media, this 'blue pencil instruction text' was replaced by tags, which indicate what the parts of the document are, rather than details of how they might be shown on some display. This lets authors avoid formatting every instance of the same kind of thing redundantly (and possibly inconsistently). It also avoids the specification of fonts and dimensions which may not apply to many users (such as those with varying-size displays, impaired vision and screen-reading software). Early markup system typically included typesetting instructions, as troff, TeX and LaTeX do, while Scribe and most modern markup systems name components, and later process those names to apply formatting or other processing, as in the case of XML. Some markup languages, such as the widely used HTML, have pre-defined presentation semantics—meaning that their specification prescribes generally how to present the structured data on particular media. Others, such as XML and its predecessor SGML, allow but do not impose such prescriptions — all of the while allowing users to define any custom document components as they wish. HyperText Markup Language (HTML), one of the document formats of the World Wide Web, is an application of SGML and XML. Other applications, such as DocBook, Open eBook, JATS and others, are heavily used in the communication of work between authors, editors, and printers. The term markup is derived from the traditional publishing practice of 'marking up' a manuscript, which involves adding handwritten annotations in the form of conventional symbolic printer's instructions — in the margins and the text of a paper or a printed manuscript. It is a jargon used in coding proof. For centuries, this task was done primarily by skilled typographers known as 'markup men' or 'd markers' who marked up text to indicate what typeface, style, and size should be applied to each part, and then passed the manuscript to others for typesetting by hand or machine. Markup was also commonly applied by editors, proofreaders, publishers, and graphic designers, and indeed by document authors, all of whom might also mark other things, such as corrections, changes, etc. There are three main general categories of electronic markup, articulated in Coombs, et al. (1987), and Bray (2003). There is considerable blurring of the lines between the types of markup. In modern word-processing systems, presentational markup is often saved in descriptive-markup-oriented systems such as XML, and then processed procedurally by implementations. The programming in procedural-markup systems, such as TeX, may be used to create higher-level markup systems that are more descriptive in nature, such as LaTeX. In the recent years, a number of small and largely unstandardized markup languages have been developed to allow authors to create formatted text via web browsers, such as the ones used in wikis and in web forums. These are sometimes called lightweight markup languages. Markdown and the markup language used by Wikipedia are examples of such wiki markup. 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 chair of the International Organization for Standardization committee that created SGML, the first standard descriptive markup language. Book designer Stanley Rice published speculation along similar lines in 1970.