Microdata is a part of the WHATWG HTML specification that defines how to include metadata within existing web page content.
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'.
Vocabularies
Microdata vocabularies do 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.
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 script and Latin alphabets. After the implementation of additional parameters from Schema's vocabulary,
indexation of information in Russian-language web-pages became more successful.
Global attributes
-
itemscope – Creates the Item and indicates that descendants of this HTML 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.
-
datetime – Indicates date or duration as specified by ISO 8601 standard.
Example
The following HTML5 markup may be found on a typical “About” page containing information about a person:
Hello, my name is John Doe, I am a graduate research assistant at
the University of Dreams.
My friends call me Johnny.
You can visit my homepage at
www.example.com/~JohnnyD.
I live at 1234 Peach Drive, Warner Robins, Georgia.
Here is the same markup with added Schema.org
Hello, my name is
John Doe,
I am a
graduate research assistant
at the
University of Dreams.
My friends call me
Johnny.
You can visit my homepage at
www.example.com/~JohnnyD.
I live at
1234 Peach Drive,
Warner Robins,
Georgia.
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.example.com/~JohnnyD
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.
Support
-
Servers: Google can
-
Browsers: , no major browser supports the Microdata DOM API.
See also
External links
