Semantic HTML

Source: Wikipedia, the free encyclopedia.
"Semantic markup" redirects here. For more general usage, see separation of content and presentation. For semantics in programming languages, see Semantics (computer science).
HTML element content categories

Semantic HTML is the use of

CSS
is used to suggest its presentation to human users.

History

HTML has included semantic markup since its inception.[1] In an HTML document, the author may, among other things, "start with a title; add headings and paragraphs; add emphasis to [the] text; add images; add links to other pages; [and] use various kinds of lists".[2]

Various versions of the HTML standard have included

Cascading Style Sheets were beginning to work in most browsers, web authors have been encouraged to avoid the use of presentational HTML markup with a view to the separation of content and presentation.[3]

In 2001,

API semantics
of the specific data they wish to mash, compare and combine.

An important type of web agent that does crawl and read web pages automatically, without prior knowledge of what it might find, is the

search facilities
.

In order for search-engine spiders to be able to rate the significance of pieces of text they find in HTML documents, and also for those creating mashups and other hybrids, as well as for more automated agents as they are developed, the semantic structures that exist in HTML need to be widely and uniformly applied to bring out the meaning of published information.[5]

While the true semantic web may depend on complex

W3C
is to slowly introduce more ways for browsers, developers, and crawlers to better distinguish between different types of data, allowing for benefits such as better display on browsers on different devices.

Presentational elements were not formally deprecated in HTML 4.01 and XHTML recommendations, but were recommended against. In HTML 5, some of those elements, such as <i> and <b>, are still specified as their meaning has been clearly defined "as to be stylistically offset from the normal prose without conveying any extra importance".[8][9]

Considerations

In cases where a document requires more precise semantics than those expressed in HTML alone, fragments of the document may be enclosed within span or div elements with meaningful class names

fragment identifier within a schema or ontology, they may link to a more defined meaning. Microformats
formalise this approach to semantics in HTML.

One important restriction of this approach is that such markup based on element inclusion must meet the well-formedness conditions. As these documents are broadly tree-structured, this means that only balanced fragments from a sub-tree can be marked up in this way.[11][12] A means of marking-up any arbitrary section of HTML would require a mechanism independent of the markup structure itself, such as XPointer.

Good semantic HTML also improves the accessibility of web documents (see also Web Content Accessibility Guidelines).[citation needed] For example, when a screen reader or audio browser can correctly ascertain the structure of a document, it will not waste the visually impaired user's time by reading out repeated or irrelevant information when it has been marked up correctly.

Google "rich snippets"

In 2010,

microdata, microformats or RDFa.[13] Microdata is specified inside itemtype and itemprop attributes added to existing HTML elements; microformat keywords are added inside class attributes as discussed above; and RDFa relies on rel, typeof and property attributes added to existing elements.[14]

See also

References

  1. ISBN 978-0062515872
    .
  2. ^ Raggett, Dave (24 April 2005). "Getting started with HTML". World Wide Web Consortium. Retrieved 8 December 2010.
  3. ^ Raggett, Dave (8 April 2002). "Adding a touch of style". World Wide Web Consortium. Retrieved 8 December 2010. This article notes that presentational HTML markup may be useful when targeting browsers "before Netscape 4.0 and Internet Explorer 4.0" which were both released in 1997.
  4. ^ Berners-Lee, Tim; Hendler, James; Lassila, Ora (2001). "The Semantic Web". Scientific American. Retrieved 2009-10-02.
  5. ^ a b Shadbolt, Nigel; Berners-Lee, Tim; Hall, Wendy (May–June 2006). "The Semantic Web Revisited" (PDF). IEEE Intelligent Systems. Retrieved 8 December 2010.
  6. ^ "Plain Old Semantic HTML (POSH)". Microformats Wiki. microformats community. April 20, 2007. Retrieved May 4, 2013.
  7. ^ Robinson, Mike. "Let's Talk about Semantics". HTML 5 Doctor. Retrieved 26 October 2015.
  8. ^ "HTML5". World Wide Web Consortium. Section 4.5.17: The i element.
  9. ^ "HTML5". World Wide Web Consortium. Section 4.5.18: The b element.
  10. ^ These class names are at best suggestive rather than formally meaningful, unless they are previously shared between both creator and consumer of the content.
  11. W3C
    .
  12. ^ "Conceitos importantes sobre HTML". Bendev Junior.
  13. ^ "Rich snippets". Webmaster Central. Retrieved 26 May 2010.
  14. ^ "Businesses and organizations - About organization information". Webmaster Central. Retrieved 26 May 2010.

External links

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