Abstract

This specification defines the HTML microdata mechanism. This mechanism allows machine-readable data to be embedded in HTML documents in an easy-to-write manner, with an unambiguous parsing model. It is compatible with numerous other data formats including RDF and JSON.

Status of This document

This section describes the status of this document at the time of its publication. Other documents may supersede this document. A list of current W3C publications and the most recently formally published revision of this technical report can be found in the W3C technical reports index at http://www.w3.org/TR/.

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The W3C HTML Working Group is the W3C working group responsible for this specification's progress along the W3C Recommendation track. This specification is the 24 May 2011 Working Draft.

Work on this specification is also done at the WHATWG. The W3C HTML working group actively pursues convergence with the WHATWG, as required by the W3C HTML working group charter.

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Table of Contents

  1. 1 Common infrastructure
    1. 1.1 Conformance requirements
    2. 1.2 HTMLPropertiesCollection
  2. 2 Introduction
    1. 2.1 Overview
    2. 2.2 The basic syntax
    3. 2.3 Typed items
    4. 2.4 Global identifiers for items
    5. 2.5 Selecting names when defining vocabularies
    6. 2.6 Using the microdata DOM API
  3. 3 Encoding microdata
    1. 3.1 The microdata model
    2. 3.2 Items
    3. 3.3 Names: the itemprop attribute
    4. 3.4 Values
    5. 3.5 Associating names with items
  4. 4 Microdata DOM API
    1. 4.1 Drag-and-drop
  5. 5 Converting HTML to other formats
    1. 5.1 JSON
    2. 5.2 RDF
      1. 5.2.1 Examples
  6. 6 IANA considerations
    1. 6.1 application/microdata+json
  7. References
  8. Acknowledgements

1 Common infrastructure

This specification is designed to be used with a host language that defines the following terms:

The host language also defines the elements used in this specification.

1.1 Conformance requirements

All diagrams, examples, and notes in this specification are non-normative, as are all sections explicitly marked non-normative. Everything else in this specification is normative.

The key words "MUST", "MUST NOT", "REQUIRED", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in the normative parts of this document are to be interpreted as described in RFC2119. For readability, these words do not appear in all uppercase letters in this specification. [RFC2119]

Requirements phrased in the imperative as part of algorithms (such as "strip any leading space characters" or "return false and abort these steps") are to be interpreted with the meaning of the key word ("must", "should", "may", etc) used in introducing the algorithm.

Conformance requirements phrased as algorithms or specific steps may be implemented in any manner, so long as the end result is equivalent. (In particular, the algorithms defined in this specification are intended to be easy to follow, and not intended to be performant.)

1.2 HTMLPropertiesCollection

The HTMLPropertiesCollection interface represents a collection of elements that add name-value pairs to a particular item in the microdata model.

interface HTMLPropertiesCollection : HTMLCollection {
  // inherits length and item()
  caller getter PropertyNodeList namedItem(in DOMString name); // overrides inherited namedItem()
  readonly attribute DOMStringList names;
};

typedef sequence<any> PropertyValueArray;

interface PropertyNodeList : NodeList {
  PropertyValueArray getValues();
};
collection . length

Returns the number of elements in the collection.

element = collection . item(index)
collection[index]
collection(index)

Returns the element with index index from the collection. The items are sorted in tree order.

Returns null if index is out of range.

propertyNodeList = collection . namedItem(name)
collection[name]
collection(name)

Returns a PropertyNodeList object containing any elements that add a property named name.

collection . names

Returns a DOMStringList with the property names of the elements in the collection.

propertyNodeList . getValues()

Returns an array of the various values that the relevant elements have.

The object's supported property indices are as defined for HTMLCollection objects.

The supported property names consist of the property names of all the elements represented by the collection.

The names attribute must return a live DOMStringList object giving the property names of all the elements represented by the collection, listed in tree order, but with duplicates removed, leaving only the first occurrence of each name. The same object must be returned each time.

The namedItem(name) method must return a PropertyNodeList object representing a live view of the HTMLPropertiesCollection object, further filtered so that the only nodes in the PropertyNodeList object are those that have a property name equal to name. The nodes in the PropertyNodeList object must be sorted in tree order, and the same object must be returned each time a particular name is queried.


Members of the PropertyNodeList interface inherited from the NodeList interface must behave as they would on a NodeList object.

The getValues method the PropertyNodeList object must return a newly constructed array whose values are the values obtained from the itemValue DOM property of each of the elements represented by the object, in tree order.

2 Introduction

2.1 Overview

This section is non-normative.

Sometimes, it is desirable to annotate content with specific machine-readable labels, e.g. to allow generic scripts to provide services that are customised to the page, or to enable content from a variety of cooperating authors to be processed by a single script in a consistent manner.

For this purpose, authors can use the microdata features described in this section. Microdata allows nested groups of name-value pairs to be added to documents, in parallel with the existing content.

2.2 The basic syntax

This section is non-normative.

At a high level, microdata consists of a group of name-value pairs. The groups are called items, and each name-value pair is a property. Items and properties are represented by regular elements.

To create an item, the itemscope attribute is used.

To add a property to an item, the itemprop attribute is used on one of the item's descendants.

Here there are two items, each of which has the property "name":

<div itemscope>
 <p>My name is <span itemprop="name">Elizabeth</span>.</p>
</div>

<div itemscope>
 <p>My name is <span itemprop="name">Daniel</span>.</p>
</div>

Properties generally have values that are strings.

Here the item has three properties:

<div itemscope>
 <p>My name is <span itemprop="name">Neil</span>.</p>
 <p>My band is called <span itemprop="band">Four Parts Water</span>.</p>
 <p>I am <span itemprop="nationality">British</span>.</p>
</div>

Properties can also have values that are URLs. This is achieved 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.

In this example, the item has one property, "image", whose value is a URL:

<div itemscope>
 <img itemprop="image" src="google-logo.png" alt="Google">
</div>

Properties can also have values that are dates, times, or dates and times. This is achieved using the time element and its datetime attribute.

In this example, the item has one property, "birthday", whose value is a date:

<div itemscope>
 I was born on <time itemprop="birthday" datetime="2009-05-10">May 10th 2009</time>.
</div>

Properties can also themselves be groups of name-value pairs, by putting the itemscope attribute on the element that declares the property.

Items that are not part of others are called top-level microdata items.

In this example, the outer item represents a person, and the inner one represents a band:

<div itemscope>
 <p>Name: <span itemprop="name">Amanda</span></p>
 <p>Band: <span itemprop="band" itemscope> <span itemprop="name">Jazz Band</span> (<span itemprop="size">12</span> players)</span></p>
</div>

The outer item here has two properties, "name" and "band". The "name" is "Amanda", and the "band" is an item in its own right, with two properties, "name" and "size". The "name" of the band is "Jazz Band", and the "size" is "12".

The outer item in this example is a top-level microdata item.

Properties that are not descendants of the element with the itemscope attribute can be associated with the item using the itemref attribute. This attribute takes a list of IDs of elements to crawl in addition to crawling the children of the element with the itemscope attribute.

This example is the same as the previous one, but all the properties are separated from their items:

<div itemscope id="amanda" itemref="a b"></div>
<p id="a">Name: <span itemprop="name">Amanda</span></p>
<div id="b" itemprop="band" itemscope itemref="c"></div>
<div id="c">
 <p>Band: <span itemprop="name">Jazz Band</span></p>
 <p>Size: <span itemprop="size">12</span> players</p>
</div>

This gives the same result as the previous example. The first item has two properties, "name", set to "Amanda", and "band", set to another item. That second item has two further properties, "name", set to "Jazz Band", and "size", set to "12".

An item can have multiple properties with the same name and different values.

This example describes an ice cream, with two flavors:

<div itemscope>
 <p>Flavors in my favorite ice cream:</p>
 <ul>
  <li itemprop="flavor">Lemon sorbet</li>
  <li itemprop="flavor">Apricot sorbet</li>
 </ul>
</div>

This thus results in an item with two properties, both "flavor", having the values "Lemon sorbet" and "Apricot sorbet".

An element introducing a property can also introduce multiple properties at once, to avoid duplication when some of the properties have the same value.

Here we see an item with two properties, "favorite-color" and "favorite-fruit", both set to the value "orange":

<div itemscope>
 <span itemprop="favorite-color favorite-fruit">orange</span>
</div>

It's important to note that there is no relationship between the microdata and the content of the document where the microdata is marked up.

There is no semantic difference, for instance, between the following two examples:

<figure>
 <img src="castle.jpeg">
 <figcaption><span itemscope><span itemprop="name">The Castle</span></span> (1986)</figcaption>
</figure>
<span itemscope><meta itemprop="name" content="The Castle"></span>
<figure>
 <img src="castle.jpeg">
 <figcaption>The Castle (1986)</figcaption>
</figure>

Both have a figure with a caption, and both, completely unrelated to the figure, have an item with a name-value pair with the name "name" and the value "The Castle". The only difference is that if the user drags the caption out of the document, in the former case, the item will be included in the drag-and-drop data. In neither case is the image in any way associated with the item.

2.3 Typed items

This section is non-normative.

The examples in the previous section show how information could be marked up on a page that doesn't expect its microdata to be re-used. Microdata is most useful, though, when it is used in contexts where other authors and readers are able to cooperate to make new uses of the markup.

For this purpose, it is necessary to give each item a type, such as "http://example.com/person", or "http://example.org/cat", or "http://band.example.net/". Types are identified as URLs.

The type for an item is given as the value of an itemtype attribute on the same element as the itemscope attribute.

Here, the item's type is "http://example.org/animals#cat":

<section itemscope itemtype="http://example.org/animals#cat">
 <h1 itemprop="name">Hedral</h1>
 <p itemprop="desc">Hedral is a male american domestic
 shorthair, with a fluffy black fur with white paws and belly.</p>
 <img itemprop="img" src="hedral.jpeg" alt="" title="Hedral, age 18 months">
</section>

In this example the "http://example.org/animals#cat" item has three properties, a "name" ("Hedral"), a "desc" ("Hedral is..."), and an "img" ("hedral.jpeg").

An item can only have one type. The type gives the context for the properties, thus defining a vocabulary: a property named "class" given for an item with the type "http://census.example/person" might refer to the economic class of an individual, while a property named "class" given for an item with the type "http://example.com/school/teacher" might refer to the classroom a teacher has been assigned.

2.4 Global identifiers for items

This section is non-normative.

Sometimes, an item gives information about a topic that has a global identifier. For example, books can be identified by their ISBN number.

Vocabularies (as identified by the itemtype attribute) can be designed such that items get associated with their global identifier in an unambiguous way by expressing the global identifiers as URLs given in an itemid attribute.

The exact meaning of the URLs given in itemid attributes depends on the vocabulary used.

Here, an item is talking about a particular book:

<dl itemscope
    itemtype="http://vocab.example.net/book"
    itemid="urn:isbn:0-330-34032-8">
 <dt>Title
 <dd itemprop="title">The Reality Dysfunction
 <dt>Author
 <dd itemprop="author">Peter F. Hamilton
 <dt>Publication date
 <dd><time itemprop="pubdate" datetime="1996-01-26">26 January 1996</time>
</dl>

The "http://vocab.example.net/book" vocabulary in this example would define that the itemid attribute takes a urn: URL pointing to the ISBN of the book.

2.5 Selecting names when defining vocabularies

This section is non-normative.

Using microdata means using a vocabulary. 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.

When designing new vocabularies, identifiers can be created either using URLs, or, for properties, as plain words (with no dots or colons). For URLs, conflicts with other vocabularies can be avoided by only using identifiers that correspond to pages that the author has control over.

For instance, if Jon and Adam both write content at example.com, at http://example.com/~jon/... and http://example.com/~adam/... respectively, then they could select identifiers of the form "http://example.com/~jon/name" and "http://example.com/~adam/name" respectively.

Properties whose names are just plain words can only be used within the context of the types for which they are intended; properties named using URLs can be reused in items of any type. If an item has no type, and is not part of another item, then if its properties have names that are just plain words, they are not intended to be globally unique, and are instead only intended for limited use. Generally speaking, authors are encouraged to use either properties with globally unique names (URLs) or ensure that their items are typed.

Here, an item is an "http://example.org/animals#cat", and most of the properties have names that are words defined in the context of that type. There are also a few additional properties whose names come from other vocabularies.

<section itemscope itemtype="http://example.org/animals#cat">
 <h1 itemprop="name http://example.com/fn">Hedral</h1>
 <p itemprop="desc">Hedral is a male american domestic
 shorthair, with a fluffy <span
 itemprop="http://example.com/color">black</span> fur with <span
 itemprop="http://example.com/color">white</span> paws and belly.</p>
 <img itemprop="img" src="hedral.jpeg" alt="" title="Hedral, age 18 months">
</section>

This example has one item with the type "http://example.org/animals#cat" and the following properties:

Property Value
name Hedral
http://example.com/fn Hedral
desc Hedral is a male american domestic shorthair, with a fluffy black fur with white paws and belly.
http://example.com/color black
http://example.com/color white
img .../hedral.jpeg

2.6 Using the microdata DOM API

This section is non-normative.

The microdata becomes even more useful when scripts can use it to expose information to the user, for example offering it in a form that can be used by other applications.

The document.getItems(typeNames) method provides access to the top-level microdata items. It returns a NodeList containing the items with the specified types, or all types if no argument is specified.

Each item is represented in the DOM by the element on which the relevant itemscope attribute is found. These elements have their element.itemScope IDL attribute set to true.

The type of items can be obtained using the element.itemType IDL attribute on the element with the itemscope attribute.

This sample shows how the getItems() method can be used to obtain a list of all the top-level microdata items of one type given in the document:

var cats = document.getItems("http://example.com/feline");

Once an element representing an item has been obtained, its properties can be extracted using the properties IDL attribute. This attribute returns an HTMLPropertiesCollection, which can be enumerated to go through each element that adds one or more properties to the item. It can also be indexed by name, which will return an object with a list of the elements that add properties with that name.

Each element that adds a property also has a itemValue IDL attribute that returns its value.

This sample gets the first item of type "http://example.net/user" and then pops up an alert using the "name" property from that item.

var user = document.getItems('http://example.net/user')[0];
alert('Hello ' + user.properties['name'][0].content + '!');

The HTMLPropertiesCollection object, when indexed by name in this way, actually returns a PropertyNodeList object with all the matching properties. The PropertyNodeList object can be used to obtain all the values at once using its getValues method, which returns an array of all the values.

In an earlier example, a "http://example.org/animals#cat" item had two "http://example.com/color" values. This script looks up the first such item and then lists all its values.

var cat = document.getItems('http://example.org/animals#cat')[0];
var colors = cat.properties['http://example.com/color'].getValues();
var result;
if (colors.length == 0) {
  result = 'Color unknown.';
} else if (colors.length == 1) {
  result = 'Color: ' + colors[0];
} else {
  result = 'Colors:';
  for (var i = 0; i < colors.length; i += 1)
    result += ' ' + colors[i];
}

It's also possible to get a list of all the property names using the object's names IDL attribute.

This example creates a big list with a nested list for each item on the page, each with of all the property names used in that item.

var outer = document.createElement('ul');
var items = document.getItems();
for (var item = 0; item < items.length; item += 1) {
  var itemLi = document.createElement('li');
  var inner = document.createElement('ul');
  for (var name = 0; name < items[item].properties.names.length; name += 1) {
    var propLi = document.createElement('li');
    propLi.appendChild(document.createTextNode(items[item].properties.names[name]));
    inner.appendChild(propLi);
  }
  itemLi.appendChild(inner);
  outer.appendChild(itemLi);
}
document.body.appendChild(outer);

If faced with the following from an earlier example:

<section itemscope itemtype="http://example.org/animals#cat">
 <h1 itemprop="name http://example.com/fn">Hedral</h1>
 <p itemprop="desc">Hedral is a male american domestic
 shorthair, with a fluffy <span
 itemprop="http://example.com/color">black</span> fur with <span
 itemprop="http://example.com/color">white</span> paws and belly.</p>
 <img itemprop="img" src="hedral.jpeg" alt="" title="Hedral, age 18 months">
</section>

...it would result in the following output:

(The duplicate occurrence of "http://example.com/color" is not included in the list.)

3 Encoding microdata

The following attributes are added as global attributes to HTML elements:

3.1 The microdata model

The microdata model consists of groups of name-value pairs known as items.

Each group is known as an item. Each item can have an item type, a global identifier (if the item type supports global identifiers for its items), and a list of name-value pairs. Each name in the name-value pair is known as a property, and each property has one or more values. Each value is either a string or itself a group of name-value pairs (an item).

An item is said to be a typed item when either it has an item type, or it is the value of a property of a typed item. The relevant type for a typed item is the item's item type, if it has one, or else is the relevant type of the item for which it is a property's value.

3.2 Items

Every HTML element may have an itemscope attribute specified. The itemscope attribute is a boolean attribute.

An element with the itemscope attribute specified creates a new item, a group of name-value pairs.


Elements with an itemscope attribute may have an itemtype attribute specified, to give the item type of the item.

The itemtype attribute, if specified, must have a value that is a valid URL that is an absolute URL for which the string "http://www.w3.org/1999/xhtml/microdata#" is not a prefix match.

The item type of an item is the value of its element's itemtype attribute, if it has one and its value is not the empty string. If the itemtype attribute is missing or its value is the empty string, the item is said to have no item type.

The item type must be a type defined in an applicable specification.

Except if otherwise specified by that specification, the URL given as the item type should not be automatically dereferenced.

A specification could define that its item type can be derefenced to provide the user with help information, for example. In fact, vocabulary authors are encouraged to provide useful information at the given URL.

Item types are opaque identifiers, and user agents must not dereference unknown item types, or otherwise deconstruct them, in order to determine how to process items that use them.

The itemtype attribute must not be specified on elements that do not have an itemscope attribute specified.


Elements with an itemscope attribute and an itemtype attribute that references a vocabulary that is defined to support global identifiers for items may also have an itemid attribute specified, to give a global identifier for the item, so that it can be related to other items on pages elsewhere on the Web.

The itemid attribute, if specified, must have a value that is a valid URL potentially surrounded by spaces.

The global identifier of an item is the value of its element's itemid attribute, if it has one, resolved relative to the element on which the attribute is specified. If the itemid attribute is missing or if resolving it fails, it is said to have no global identifier.

The itemid attribute must not be specified on elements that do not have both an itemscope attribute and an itemtype attribute specified, and must not be specified on elements with an itemscope attribute whose itemtype attribute specifies a vocabulary that does not support global identifiers for items, as defined by that vocabulary's specification.


Elements with an itemscope attribute may have an itemref attribute specified, to give a list of additional elements to crawl to find the name-value pairs of the item.

The itemref attribute, if specified, must have a value that is an unordered set of unique space-separated tokens that are case-sensitive, consisting of IDs of elements in the same home subtree.

The itemref attribute must not be specified on elements that do not have an itemscope attribute specified.

3.3 Names: the itemprop attribute

Every HTML element may have an itemprop attribute specified, if doing so adds a property to one or more items (as defined below).

The itemprop attribute, if specified, must have a value that is an unordered set of unique space-separated tokens that are case-sensitive, representing the names of the name-value pairs that it adds. The attribute's value must have at least one token.

Each token must be either:

Specifications that introduce defined property names that are not absolute URLs must ensure all such property names contain no U+002E FULL STOP characters (.), no U+003A COLON characters (:), and no space characters.

When an element with an itemprop attribute adds a property to multiple items, the requirement above regarding the tokens applies for each item individually.

The property names of an element are the tokens that the element's itemprop attribute is found to contain when its value is split on spaces, with the order preserved but with duplicates removed (leaving only the first occurrence of each name).

Within an item, the properties are unordered with respect to each other, except for properties with the same name, which are ordered in the order they are given by the algorithm that defines the properties of an item.

In the following example, the "a" property has the values "1" and "2", in that order, but whether the "a" property comes before the "b" property or not is not important:

<div itemscope>
 <p itemprop="a">1</p>
 <p itemprop="a">2</p>
 <p itemprop="b">test</p>
</div>

Thus, the following is equivalent:

<div itemscope>
 <p itemprop="b">test</p>
 <p itemprop="a">1</p>
 <p itemprop="a">2</p>
</div>

As is the following:

<div itemscope>
 <p itemprop="a">1</p>
 <p itemprop="b">test</p>
 <p itemprop="a">2</p>
</div>

And the following:

<div itemscope itemref="x">
 <p itemprop="b">test</p>
 <p itemprop="a">2</p>
</div>
<div id="x">
 <p itemprop="a">1</p>
</div>

3.4 Values

The property value of a name-value pair added by an element with an itemprop attribute depends on the element, as follows:

If the element also has an itemscope attribute

The value is the item created by the element.

If the element is a meta element

The value is the value of the element's content attribute, if any, or the empty string if there is no such attribute.

If the element is an audio, embed, iframe, img, source, track, or video element

The value is the absolute URL that results from resolving the value of the element's src attribute relative to the element at the time the attribute is set, or the empty string if there is no such attribute or if resolving it results in an error.

If the element is an a, area, or link element

The value is the absolute URL that results from resolving the value of the element's href attribute relative to the element at the time the attribute is set, or the empty string if there is no such attribute or if resolving it results in an error.

If the element is an object element

The value is the absolute URL that results from resolving the value of the element's data attribute relative to the element at the time the attribute is set, or the empty string if there is no such attribute or if resolving it results in an error.

If the element is a time element with a datetime attribute

The value is the value of the element's datetime attribute.

Otherwise

The value is the element's textContent.

The URL property elements are the a, area, audio, embed, iframe, img, link, object, source, track, and video elements.

If a property's value is an absolute URL, the property must be specified using a URL property element.

If a property's value represents a date, time, or global date and time, the property must be specified using the datetime attribute of a time element.

3.5 Associating names with items

To find the properties of an item defined by the element root, the user agent must try to crawl the properties of the element root, with an empty list as the value of memory: if this fails, then the properties of the item defined by the element root is an empty list; otherwise, it is the returned list.

To crawl the properties of an element root with a list memory, the user agent must run the following steps. These steps either fail or return a list with a count of errors. The count of errors is used as part of the authoring conformance criteria below.

  1. If root is in memory, then the algorithm fails; abort these steps.

  2. Collect all the elements in the item root; let results be the resulting list of elements, and errors be the resulting count of errors.

  3. Remove any elements from results that do not have an itemprop attribute specified.

  4. Let new memory be a new list consisting of the old list memory with the addition of root.

  5. For each element in results that has an itemscope attribute specified, crawl the properties of the element, with new memory as the memory. If this fails, then remove the element from results and increment errors. (If it succeeds, the return value is discarded.)

  6. Sort results in tree order.

  7. Return results and errors.

To collect all the elements in the item root, the user agent must run these steps. They return a list of elements and a count of errors.

  1. Let results and pending be empty lists of elements.

  2. Let errors be zero.

  3. Add all the children elements of root to pending.

  4. If root has an itemref attribute, split the value of that itemref attribute on spaces. For each resulting token ID, if there is an element in the home subtree of root with the ID ID, then add the first such element to pending.

  5. Loop: Remove an element from pending and let current be that element.

  6. If current is already in results, increment errors.

  7. If current is not already in results and current does not have an itemscope attribute, then: add all the child elements of current to pending.

  8. If current is not already in results, then: add current to results.

  9. End of loop: If pending is not empty, return to the step labeled loop.

  10. Return results and errors.

An item is a top-level microdata item if its element does not have an itemprop attribute.

An item is a used microdata item if it is a top-level microdata item, or if it has an itemprop attribute and would be found to be the property of an item that is itself a used microdata item.

All items in a document must be used microdata items.

A document must not contain any elements that have an itemprop attribute that would not be found to be a property of any of the items in that document were their properties all to be determined.

A document must not contain any items for which crawling the properties of the element, with an empty list as the value of memory, either fails or returns an error count other than zero.

The algorithms in this section are especially inefficient, in the interests of keeping them easy to understand. Implementors are strongly encouraged to refactor and optimize them in their user agents.

In this example, a single license statement is applied to two works, using itemref from the items representing the works:

<!DOCTYPE HTML>
<html>
 <head>
  <title>Photo gallery</title>
 </head>
 <body>
  <h1>My photos</h1>
  <figure itemscope itemtype="http://n.whatwg.org/work" itemref="licenses">
   <img itemprop="work" src="images/house.jpeg" alt="A white house, boarded up, sits in a forest.">
   <figcaption itemprop="title">The house I found.</figcaption>
  </figure>
  <figure itemscope itemtype="http://n.whatwg.org/work" itemref="licenses">
   <img itemprop="work" src="images/mailbox.jpeg" alt="Outside the house is a mailbox. It has a leaflet inside.">
   <figcaption itemprop="title">The mailbox.</figcaption>
  </figure>
  <footer>
   <p id="licenses">All images licensed under the <a itemprop="license"
   href="http://www.opensource.org/licenses/mit-license.php">MIT
   license</a>.</p>
  </footer>
 </body>
</html>

The above results in two items with the type "http://n.whatwg.org/work", one with:

work
images/house.jpeg
title
The house I found.
license
http://www.opensource.org/licenses/mit-license.php

...and one with:

work
images/mailbox.jpeg
title
The mailbox.
license
http://www.opensource.org/licenses/mit-license.php

4 Microdata DOM API

[Supplemental] interface HTMLDocument { 
  NodeList getItems(in optional DOMString typeNames); // microdata
};

[Supplemental] interface HTMLElement {
  // microdata 
           attribute boolean itemScope;
           attribute DOMString itemType;
           attribute DOMString itemId;
  [PutForwards=value] readonly attribute DOMSettableTokenList itemRef;
  [PutForwards=value] readonly attribute DOMSettableTokenList itemProp;
  readonly attribute HTMLPropertiesCollection properties;
           attribute any itemValue;
};
document . getItems( [ types ] )

Returns a NodeList of the elements in the Document that create items, that are not part of other items, and that are of one of the types given in the argument, if any are listed.

The types argument is interpreted as a space-separated list of types.

element . properties

If the element has an itemscope attribute, returns an HTMLPropertiesCollection object with all the element's properties. Otherwise, an empty HTMLPropertiesCollection object.

element . itemValue [ = value ]

Returns the element's value.

Can be set, to change the element's value. Setting the value when the element has no itemprop attribute or when the element's value is an item throws an INVALID_ACCESS_ERR exception.

The document.getItems(typeNames) method takes an optional string that contains an unordered set of unique space-separated tokens that are case-sensitive, representing types. When called, the method must return a live NodeList object containing all the elements in the document, in tree order, that are each top-level microdata items with a type equal to one of the types specified in that argument, having obtained the types by splitting the string on spaces. If there are no tokens specified in the argument, or if the argument is missing, then the method must return a NodeList containing all the top-level microdata items in the document. When the method is invoked on a Document object again with the same argument, the user agent may return the same object as the object returned by the earlier call. In other cases, a new NodeList object must be returned.

The itemScope IDL attribute on HTML elements must reflect the itemscope content attribute. The itemType IDL attribute on HTML elements must reflect the itemtype content attribute, as if it was a regular string attribute, not a URL string attribute. The itemId IDL attribute on HTML elements must reflect the itemid content attribute. The itemProp IDL attribute on HTML elements must reflect the itemprop content attribute. The itemRef IDL attribute on HTML elements must reflect the itemref content attribute.

The properties IDL attribute on HTML elements must return an HTMLPropertiesCollection rooted at the Document node, whose filter matches only elements that have property names and are the properties of the item created by the element on which the attribute was invoked, while that element is an item, and matches nothing the rest of the time.

The itemValue IDL attribute's behavior depends on the element, as follows:

If the element has no itemprop attribute

The attribute must return null on getting and must throw an INVALID_ACCESS_ERR exception on setting.

If the element has an itemscope attribute

The attribute must return the element itself on getting and must throw an INVALID_ACCESS_ERR exception on setting.

If the element is a meta element

The attribute must act as it would if it was reflecting the element's content content attribute.

If the element is an audio, embed, iframe, img, source, track, or video element

The attribute must act as it would if it was reflecting the element's src content attribute.

If the element is an a, area, or link element

The attribute must act as it would if it was reflecting the element's href content attribute.

If the element is an object element

The attribute must act as it would if it was reflecting the element's data content attribute.

If the element is a time element with a datetime attribute

The attribute must act as it would if it was reflecting the element's datetime content attribute.

Otherwise

The attribute must act the same as the element's textContent attribute.

When the itemValue IDL attribute is reflecting a content attribute or acting like the element's textContent attribute, the user agent must, on setting, convert the new value to the IDL DOMString value before using it according to the mappings described above.

In this example, a script checks to see if a particular element element is declaring a particular property, and if it is, it increments a counter:

if (element.itemProp.contains('color'))
  count += 1;

This script iterates over each of the values of an element's itemref attribute, calling a function for each referenced element:

for (var index = 0; index < element.itemRef.length; index += 1)
  process(document.getElementById(element.itemRef[index]));

4.1 Drag-and-drop

The drag-and-drop initialization steps are:

  1. The user agent must take the list of dragged nodes and extract the microdata from those nodes into a JSON form, and then must add the resulting string to the dataTransfer member, associated with the application/microdata+json format.

5 Converting HTML to other formats

5.1 JSON

Given a list of nodes nodes in a Document, a user agent must run the following algorithm to extract the microdata from those nodes into a JSON form:

  1. Let result be an empty object.

  2. Let items be an empty array.

  3. For each node in nodes, check if the element is a top-level microdata item, and if it is then get the object for that element and add it to items.

  4. Add an entry to result called "items" whose value is the array items.

  5. Return the result of serializing result to JSON.

When the user agent is to get the object for an item item, it must run the following substeps:

  1. Let result be an empty object.

  2. If the item has an item type, add an entry to result called "type" whose value is the item type of item.

  3. If the item has an global identifier, add an entry to result called "id" whose value is the global identifier of item.

  4. Let properties be an empty object.

  5. For each element element that has one or more property names and is one of the properties of the item item, in the order those elements are given by the algorithm that returns the properties of an item, run the following substeps:

    1. Let value be the property value of element.

    2. If value is an item, then get the object for value, and then replace value with the object returned from those steps.

    3. For each name name in element's property names, run the following substeps:

      1. If there is no entry named name in properties, then add an entry named name to properties whose value is an empty array.

      2. Append value to the entry named name in properties.

  6. Add an entry to result called "properties" whose value is the object properties.

  7. Return result.

5.2 RDF

To convert a Document to RDF, a user agent must run the following algorithm:

  1. If the title element is not null, then generate the following triple:

    subject
    the document's current address
    predicate
    http://purl.org/dc/terms/title
    object
    the concatenation of the data of all the child text nodes of the title element, in tree order, as a plain literal, with the language information set from the language of the title element, if it is not unknown.
  2. For each a, area, and link element in the Document, run these substeps:

    1. If the element does not have a rel attribute, then skip this element.

    2. If the element does not have an href attribute, then skip this element.

    3. If resolving the element's href attribute relative to the element is not successful, then skip this element.

    4. Otherwise, split the value of the element's rel attribute on spaces, obtaining list of tokens.

    5. Convert each token in list of tokens that does not contain a U+003A COLON characters (:) to ASCII lowercase.

    6. Coalesce duplicate tokens in list of tokens.

    7. If list of tokens contains both the tokens alternate and stylesheet, then remove them both and replace them with the single (uppercase) token ALTERNATE-STYLESHEET.

    8. For each token token in list of tokens that contains no U+003A COLON characters (:), generate the following triple:

      subject
      the document's current address
      predicate
      the fragment-escaped concatenation of the string "http://www.w3.org/1999/xhtml/vocab#" and token
      object
      the absolute URL that results from resolving the value of the element's href attribute relative to the element

      For each token token in list of tokens that is an absolute URL, generate the following triple:

      subject
      the document's current address
      predicate
      token
      object
      the absolute URL that results from resolving the value of the element's href attribute relative to the element
  3. For each meta element in the Document that has a name attribute and a content attribute, if the value of the name attribute contains no U+003A COLON characters (:), generate the following triple:

    subject
    the document's current address
    predicate
    the fragment-escaped concatenation of the string "http://www.w3.org/1999/xhtml/vocab#" and the value of the element's name attribute, converted to ASCII lowercase
    object
    the value of the element's content attribute, as a plain literal, with the language information set from the language of the element, if it is not unknown

    For each meta element in the Document that has a name attribute and a content attribute, if the value of the name attribute is an absolute URL, generate the following triple:

    subject
    the document's current address
    predicate
    the value of the element's name attribute
    object
    the value of the element's content attribute, as a plain literal, with the language information set from the language of the element, if it is not unknown
  4. For each blockquote and q element in the Document that has a cite attribute that resolves successfully relative to the element, generate the following triple:

    subject
    the document's current address
    predicate
    http://purl.org/dc/terms/source
    object
    the absolute URL that results from resolving the value of the element's cite attribute relative to the element
  5. Let memory be a mapping of items to subjects, initially empty.

  6. For each element that is also a top-level microdata item, run the following steps:

    1. Generate the triples for the item. Pass a reference to memory as the item/subject list. Let result be the subject returned.

    2. Generate the following triple:

      subject
      the document's current address
      predicate
      http://www.w3.org/1999/xhtml/microdata#item
      object
      result

When the user agent is to generate the triples for an item item, given a reference to an item/subject list memory, and optionally given a fallback type fallback type and property name fallback name, it must run the following steps:

  1. If there is an entry for item in memory, then let subject be the subject of that entry. Otherwise, if item has a global identifier and that global identifier is an absolute URL, let subject be that global identifier. Otherwise, let subject be a new blank node.

  2. Add a mapping from item to subject in memory, if there isn't one already.

  3. If item has an item type and that item type is an absolute URL, let type be that item type. Otherwise, let type be the empty string.

  4. If type is not the empty string, run the following steps:

    1. Generate the following triple:

      subject
      subject
      predicate
      http://www.w3.org/1999/02/22-rdf-syntax-ns#type
      object
      type
    2. If type does not contain a U+0023 NUMBER SIGN character (#), then append a U+0023 NUMBER SIGN character (#) to type.

    3. If type does not have a U+003A COLON character (:) after its U+0023 NUMBER SIGN character (#), append a U+003A COLON character (:) to type.

  5. If type is the empty string, but fallback type is not, run the following substeps:

    1. Let type have the value of fallback type.

    2. If type does not contain a U+0023 NUMBER SIGN character (#), then append a U+0023 NUMBER SIGN character (#) to type.

    3. If type does not have a U+003A COLON character (:) after its U+0023 NUMBER SIGN character (#), append a U+003A COLON character (:) to type.

    4. If the last character of type is not a U+003A COLON character (:), append a U+0025 PERCENT SIGN character (%), a U+0032 DIGIT TWO character (2), and a U+0030 DIGIT ZERO character (0) to type.

    5. Append the fragment-escaped value of fallback name to type.

  6. For each element element that has one or more property names and is one of the properties of the item item, in the order those elements are given by the algorithm that returns the properties of an item, run the following substep:

    1. For each name name in element's property names, run the following substeps:

      1. If type is the empty string and name is not an absolute URL, then abort these substeps.

      2. Let value be the property value of element.

      3. If value is an item, then generate the triples for value. Pass a reference to memory as the item/subject list, and pass type as the fallback type and name as the fallback property name. Replace value by the subject returned from those steps.

      4. Otherwise, if element is not one of the URL property elements, let value be a plain literal, with the language information set from the language of the element, if it is not unknown.

      5. If name is an absolute URL

        Let predicate be name.

        If name contains no U+003A COLON characters (:)
        1. Let s be type.

        2. If the last character of s is not a U+003A COLON character (:), append a U+0025 PERCENT SIGN character (%), a U+0032 DIGIT TWO character (2), and a U+0030 DIGIT ZERO character (0) to s.

        3. Append the fragment-escaped value of name to s.

        4. Let predicate be the concatenation of the string "http://www.w3.org/1999/xhtml/microdata#" and the fragment-escaped value of s.

          For example if the string s is "http://example.com/a#:q%20r", the resulting predicate would be "http://www.w3.org/1999/xhtml/microdata#http://example.com/a%23:q%20r".

      6. Generate the following triple:

        subject
        subject
        predicate
        predicate
        object
        value
  7. Return subject.

5.2.1 Examples

This section is non-normative.

Here is an example of some HTML using Microdata to express RDF statements:

<dl itemscope
    itemtype="http://purl.org/vocab/frbr/core#Work"
    itemid="http://books.example.com/works/45U8QJGZSQKDH8N">
 <dt>Title</dt>
 <dd><cite itemprop="http://purl.org/dc/terms/title">Just a Geek</cite></dd>
 <dt>By</dt>
 <dd><span itemprop="http://purl.org/dc/elements/1.1/creator">Wil Wheaton</span></dd>
 <dt>Format</dt>
 <dd itemprop="http://purl.org/vocab/frbr/core#realization"
     itemscope
     itemtype="http://purl.org/vocab/frbr/core#Expression"
     itemid="http://books.example.com/products/9780596007683.BOOK">
  <link itemprop="http://purl.org/dc/terms/type" href="http://books.example.com/product-types/BOOK">
  Print
 </dd>
 <dd itemprop="http://purl.org/vocab/frbr/core#realization"
     itemscope
     itemtype="http://purl.org/vocab/frbr/core#Expression"
     itemid="http://books.example.com/products/9780596802189.EBOOK">
  <link itemprop="http://purl.org/dc/terms/type" href="http://books.example.com/product-types/EBOOK">
  Ebook
 </dd>
</dl>

This is equivalent to the following Turtle:

@prefix dct: <http://purl.org/dc/terms/> .
 @prefix dce: <http://purl.org/dc/elements/1.1/> .
 @prefix frbr: <http://purl.org/vocab/frbr/core#> .

<http://books.example.com/works/45U8QJGZSQKDH8N> a frbr:Work ;
     dce:creator "Wil Wheaton"@en ;
     dct:title "Just a Geek"@en ;
     frbr:realization <http://books.example.com/products/9780596007683.BOOK>,
         <http://books.example.com/products/9780596802189.EBOOK> .

<http://books.example.com/products/9780596007683.BOOK> a frbr:Expression ;
     dct:type <http://books.example.com/product-types/BOOK> .

<http://books.example.com/products/9780596802189.EBOOK> a frbr:Expression ;
     dct:type <http://books.example.com/product-types/EBOOK> .

The following snippet of HTML has microdata for two people with the same address:

<p>
 Both
 <span itemscope itemtype="http://microformats.org/profile/hcard" itemref="home"><span itemprop="fn"
 ><span itemprop="n" itemscope><span itemprop="given-name">Princeton</span></span></span></span>
 and
 <span itemscope itemtype="http://microformats.org/profile/hcard" itemref="home"><span itemprop="fn"
 ><span itemprop="n" itemscope><span itemprop="given-name">Trekkie</span></span></span></span>
 live at
 <span id="home" itemprop="adr" itemscope><span itemprop="street-address">Avenue Q</span>.</span>
</p>

It generates these triples expressed in Turtle (including a triple that in this case is expressed twice, though that is not meaningful in RDF):

@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
@prefix dct: <http://purl.org/dc/terms/> .
@prefix hcard: <http://www.w3.org/1999/xhtml/microdata#http://microformats.org/profile/hcard%23:> .

<> <http://www.w3.org/1999/xhtml/microdata#item> _:n0 ;
   <http://www.w3.org/1999/xhtml/microdata#item> _:n1 .
_:n0  rdf:type <http://microformats.org/profile/hcard> ;
      hcard:fn "Princeton" ;
      hcard:n _:n0a
      hcard:adr _:n2 .
_:n0a hcard:n%20given-name "Princeton" .
_:n1  rdf:type <http://microformats.org/profile/hcard> ;
      hcard:fn "Trekkie" ;
      hcard:n _:n1a
      hcard:adr _:n2 .
_:n1a hcard:n%20given-name "Trekkie" .
_:n2  hcard:adr%20street-address "Avenue Q" ;
      hcard:adr%20street-address "Avenue Q" .

6 IANA considerations

6.1 application/microdata+json

This registration is for community review and will be submitted to the IESG for review, approval, and registration with IANA.

Type name:
application
Subtype name:
microdata+json
Required parameters:
Same as for application/json [JSON]
Optional parameters:
Same as for application/json [JSON]
Encoding considerations:
Always UTF-8.
Security considerations:
Same as for application/json [JSON]
Interoperability considerations:
Same as for application/json [JSON]
Published specification:
Labeling a resource with the application/microdata+json type asserts that the resource is a JSON text that consists of an object with a single entry called "items" consisting of an array of entries, each of which consists of an object with an entry called "id" whose value is a string, an entry called "type" whose value is another string, and an entry called "properties" whose value is an object whose entries each have a value consisting of an array of either objects or strings, the objects being of the same form as the objects in the aforementioned "items" entry. As such, the relevant specifications are the JSON specification and this specification. [JSON]
Applications that use this media type:
Same as for application/json [JSON]
Additional information:
Magic number(s):
Same as for application/json [JSON]
File extension(s):
Same as for application/json [JSON]
Macintosh file type code(s):
Same as for application/json [JSON]
Person & email address to contact for further information:
Ian Hickson <ian@hixie.ch>
Intended usage:
Common
Restrictions on usage:
No restrictions apply.
Author:
Ian Hickson <ian@hixie.ch>
Change controller:
W3C

Fragment identifiers used with application/microdata+json resources have the same semantics as when used with application/json (namely, at the time of writing, no semantics at all). [JSON]

References

All references are normative unless marked "Non-normative".

[HTML5]
(Non-normative) HTML5, I. Hickson. W3C.
[JSON]
The application/json Media Type for JavaScript Object Notation (JSON), D. Crockford. IETF.
[RFC2119]
Key words for use in RFCs to Indicate Requirement Levels, S. Bradner. IETF.
[WEBIDL]
Web IDL, C. McCormack. W3C.

Acknowledgements

Thanks to the participants of the microdata usability study for allowing us to use their mistakes as a guide for designing the microdata feature.

For a full list of acknowledgements, please see the HTML5 specification. [HTML5]