Structured document
Encyclopedia
A structured document is an electronic document
Electronic document
An electronic document is any electronic media content that are intended to be used in either an electronic form or as printed output....

 where some method of embedded coding, such as markup
Markup language
A markup language is a modern system for annotating a text in a way that is syntactically distinguishable from that text. The idea and terminology evolved from the "marking up" of manuscripts, i.e. the revision instructions by editors, traditionally written with a blue pencil on authors' manuscripts...

, is used to give the whole, and parts, of the document various structural meanings according to a schema
Database schema
A database schema of a database system is its structure described in a formal language supported by the database management system and refers to the organization of data to create a blueprint of how a database will be constructed...

. A structured document whose markup doesn't break the schema it is designed to conform to and which obeys the syntax
Syntax
In linguistics, syntax is the study of the principles and rules for constructing phrases and sentences in natural languages....

 rules of its markup language
Markup language
A markup language is a modern system for annotating a text in a way that is syntactically distinguishable from that text. The idea and terminology evolved from the "marking up" of manuscripts, i.e. the revision instructions by editors, traditionally written with a blue pencil on authors' manuscripts...

 is "well-formed".
As of 2009 the most widely used markup language
Markup language
A markup language is a modern system for annotating a text in a way that is syntactically distinguishable from that text. The idea and terminology evolved from the "marking up" of manuscripts, i.e. the revision instructions by editors, traditionally written with a blue pencil on authors' manuscripts...

, in all its evolving forms, is HTML
HTML
HyperText Markup Language is the predominant markup language for web pages. HTML elements are the basic building-blocks of webpages....

, which is used to structure documents according to various Document Type Definition (DTD)
Document Type Definition
Document Type Definition is a set of markup declarations that define a document type for SGML-family markup languages...

 schema defined and described by the W3C, which continually reviews, refines and evolves the specifications.

Structural semantics

In writing structured documents the focus is on encoding the logical structure of a document, with no explicit concern in the structural markup for its presentation to humans by printed pages, screens or other means. Structured documents, especially well formed ones, can easily be processed by computer systems to extract and present metadata
Metadata
The term metadata is an ambiguous term which is used for two fundamentally different concepts . Although the expression "data about data" is often used, it does not apply to both in the same way. Structural metadata, the design and specification of data structures, cannot be about data, because at...

 about the document. In most Wikipedia articles for example, a table of contents is automatically generated from the different heading tags in the body of the document. Popular word processor
Word processor
A word processor is a computer application used for the production of any sort of printable material....

s can have such a function available.

In HTML
HTML
HyperText Markup Language is the predominant markup language for web pages. HTML elements are the basic building-blocks of webpages....

 a part of the logical structure of a document may be the document body; , containing a first level heading;

, and a paragraph;

.

Structured document

A structured document is an electronic document where some method of embedded coding, such as markup, is used to give the whole, and parts, of the document various structural meanings according to a schema.





One of the most attractive features of structured documents is that they can be reused in many contexts and presented in various ways on mobile phones, TV screens, speech synthesisers, and any other device which can be programmed to process them.

Other semantics

Other meaning can be ascribed to text which isn't structural. In the HTML
HTML
HyperText Markup Language is the predominant markup language for web pages. HTML elements are the basic building-blocks of webpages....

 fragment above, there is semantic markup which has nothing to do with structure; the first of these, the tag, means that the enclosed text should be given a strong emphasis. In visual terms this is equivalent to the bold, tag, but in speech synthesisers this means a voice inflection giving strong emphasis is used. The term semantic markup excludes markup like the bold tag which has no meaning other than an instruction to a visual display. The strong tag means that the presentation of the enclosed text should have a strong emphasis in all presentation forms, not just visual.

The anchor tag is a more obvious example of semantic markup unconcerned with structure, with its href attribute set it means that the text it surrounds is a hyperlink
Hyperlink
In computing, a hyperlink is a reference to data that the reader can directly follow, or that is followed automatically. A hyperlink points to a whole document or to a specific element within a document. Hypertext is text with hyperlinks...

.

The original HTML specification had no tags which gave presentational semantics, i.e. there were no tags to give bold or italic text, or to alter font sizes or which had other effects on the presentation. Modern versions of markup languages discourage such markup in favour of style sheets. Different style sheets can be attached to any markup, semantic or presentational, to produce different presentations. In HTML
HTML
HyperText Markup Language is the predominant markup language for web pages. HTML elements are the basic building-blocks of webpages....

, tags such as; ,
, , and others do not have a structural meaning, but do have a meaning.
The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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