Microdata (HTML)

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Microdata is a WHATWG HTML specification used to nest metadata within existing content on web pages. Search engines, web crawlers, and browsers can extract and process Microdata from a web page and use it to provide a richer browsing experience for users. Search engines benefit greatly from direct access to this structured data because it allows them to understand the information on web pages and provide more relevant results to users. Microdata uses a supporting vocabulary to describe an item and name-value pairs to assign values to its properties. Microdata is an attempt to provide a simpler way of annotating HTML elements with machine-readable tags than the similar approaches of using RDFa and microformats.

In 2013, because the W3C HTML Working Group failed to find someone to serve as an editor for the Microdata HTML specification, its development was terminated with a 'Note'. However, since that time, two new editors were selected, and four newer versions of the working draft have been published, the most recent being W3C Working Draft 10 October 2017.

Video Microdata (HTML)

Vocabularies

Microdata vocabularies does not provide the semantics, or meaning of an Item. Web developers can design a custom vocabulary or use vocabularies available on the web. A collection of commonly used markup vocabularies are provided by Schema.org schemas which include: Person, "Place", Event, Organization, Product, Review, Review-aggregate, Breadcrumb, Offer, Offer-aggregate. The website schema.org was established by search engine operators like Google, Microsoft, Yahoo!, and Yandex, which use microdata markup to improve search results.

For some purposes, an ad-hoc vocabulary is adequate. For others, a vocabulary will need to be designed. Where possible, authors are encouraged to re-use existing vocabularies, as this makes content re-use easier.

Maps Microdata (HTML)

Localization

In some cases, search engines covering specific regions may provide locally-specific extensions of microdata. For example, Yandex, a major search engine in Russia, supports microformats such as hCard (company contact information), hRecipe (food recipe), hReview (market reviews) and hProduct (product data) and provides its own format for definition of the terms and encyclopedic articles. This extension was made in order to solve transliteration problems between the Cyrillic and Latin alphabets. After the implementation of additional parameters from Schema's vocabulary, indexation of information in Russian-language web-pages became more successful.

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Global attributes

• itemscope - Creates the Item and indicates that descendants of this element contain information about it.
• itemtype - A valid URL of a vocabulary that describes the item and its properties context.
• itemid - Indicates a unique identifier of the item.
• itemprop - Indicates that its containing tag holds the value of the specified item property. The property's name and value context are described by the item's vocabulary. Properties values usually consist of string values, but can also use URLs using the a element and its href attribute, the img element and its src attribute, or other elements that link to or embed external resources.
• itemref - Properties that are not descendants of the element with the itemscope attribute can be associated with the item using this attribute. Provides a list of element ids (not itemids) with additional properties elsewhere in the document.

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Example

The following HTML5 markup may be found on a typical "About" page containing information about a person:

Here is the same markup with added Schema.org Microdata:

As the above example shows, Microdata items can be nested. In this case an item of type http://schema.org/PostalAddress is nested inside an item of type http://schema.org/Person.

The following text shows how Google parses the Microdata from the above example code. Developers can test pages containing Microdata using Google's Rich Snippet Testing Tool.

Item     Type: http://schema.org/Person     name = John Doe     jobTitle = graduate research assistant     affiliation = University of Dreams     additionalName = Johnny     url = http://www.johnnyd.com/     address = Item(1)  Item 1     Type: http://schema.org/PostalAddress     streetAddress = 1234 Peach Drive     addressLocality = Warner Robins     addressRegion = Georgia  

The same machine-readable terms can be used not only in HTML Microdata, but also in other annotations such as RDFa or JSON-LD in the markup, or in an external RDF file in a serialization such as RDF/XML, Notation3, or Turtle.

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Support

• Servers: Google can use microdata in its result pages. It is the preferred snippet format for the Google+ social network.
• Browsers: As of December 2013, notable browsers that added support for the Microdata DOM API, are:. As of April 2018, Microdata DOM API is deprecated according to Mozilla .

• Libraries: MicrodataJS is a JavaScript library and jQuery plugin that emulates the DOM API.

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See also

• Semantic web
• Microformat

• RDFa Lite
• JSON-LD

• Semantic HTML
• Semantic social network

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References

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External links

• Microdata -- HTML Draft Standard, WHATWG 
• W3C HTML Microdata Working Group Note, W3C 
• Almaer, Dion (2009-05-11), Hixie discusses the addition of HTML5 "microdata", Ajaxian 
• HTML5 Microdata Specs, Data-Vocabulary.org 

Source of article : Wikipedia