Copyright © 2013 W3C® (MIT, ERCIM, Keio, Beihang), All Rights Reserved. W3C liability, trademark and document use rules apply.
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.
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 latest revision of this technical report can be found in the W3C technical reports index at http://www.w3.org/TR/.
This document was edited in place on 23 June 2014 to fix a wrong "Previous Version" link.
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The bulk of the text of this specification is also available in the WHATWG HTML Living Standard, under a license that permits reuse of the specification text.
Publication as a Working Group Note does not imply endorsement by the W3C Membership. This is a draft document and may be updated, replaced or obsoleted by other documents at any time. It is inappropriate to cite this document as other than work in progress.
The latest stable version of the editor's draft of this specification is always available on the W3C HTML git repository.
The W3C HTML Working Group is the W3C working group responsible for this specification's progress. This specification is the 29 October 2013 Working Group Note.
This specification is an extension to the HTML5 language. All normative content in the HTML5 specification, unless specifically overridden by this specification, is intended to be the basis for this specification.
This document was produced by a group operating under the 5 February 2004 W3C Patent Policy. W3C maintains a public list of any patent disclosures made in connection with the deliverables of the group; that page also includes instructions for disclosing a patent. An individual who has actual knowledge of a patent which the individual believes contains Essential Claim(s) must disclose the information in accordance with section 6 of the W3C Patent Policy.
This specification depends on the Web IDL and HTML5 specifications. [WEBIDL] [HTML5]
This specification relies heavily on the HTML5 specification to define underlying terms.
HTML5 defines the concept of DOM collections and the
HTMLCollection interface, as well as the
concept of IDL attributes reflecting
content attributes. It also defines tree order and the
concept of a node's home subtree.
HTML5 defines the terms URL, valid URL, absolute URL, and resolve a URL.
HTML5 defines the terms alphanumeric ASCII characters, space characters split a string on spaces, converted to ASCII uppercase, and prefix match.
HTML5 defines the meaning of the term HTML elements, as
well as all the elements referenced in this specification. It also
defines the HTMLElement and
HTMLDocument interfaces. It defines the
specific concept of the title element in the
context of an HTMLDocument. In the context of content
models it defines the terms flow content and
phrasing content. It also defines what an element's ID or language is in HTML.
HTML5 defines the set of global attributes, as well as terms used in describing attributes and their processing, such as the concept of a boolean attribute, of an unordered set of unique space-separated tokens, of a valid non-negative integer, of a date, a time, a global date and time, a valid date string, and a valid global date and time string.
HTML5 defines what the document's current address is.
Finally, HTML5 also defines the concepts of drag-and-drop initialization steps and of the list of dragged nodes, which come up in the context of drag-and-drop interfaces.
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", "MAY", and "OPTIONAL" in the normative parts of this document are to be interpreted as described in RFC2119. The key word "OPTIONALLY" in the normative parts of this document is to be interpreted with the same normative meaning as "MAY" and "OPTIONAL". 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.
For example, were the spec to say:
To eat an orange, the user must: 1. Peel the orange. 2. Separate each slice of the orange. 3. Eat the orange slices.
...it would be equivalent to the following:
To eat an orange: 1. The user must peel the orange. 2. The user must separate each slice of the orange. 3. The user must eat the orange slices.
Here the key word is "must".
The former (imperative) style is generally preferred in this specification for stylistic reasons.
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.)
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.
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>
Markup without microdata attributes has no effect on microdata.
These two examples are exactly equivalent, at a microdata level, as the previous two examples respectively:
<div itemscope> <p>My <em>name</em> is <span itemprop="name">E<strong>liz</strong>abeth</span>.</p> </div> <section> <div itemscope> <aside> <p>My name is <span itemprop="name"><a href="/?user=daniel">Daniel</a></span>.</p> </aside> </div> </section>
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>
When a string value is a URL, it is expressed 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>
When a string value is in some machine-readable format unsuitable
for human consumption, it is expressed using the value attribute of the
data element, with the human-readable version given in
the element's contents.
Here, there is an item with a property whose value is a product ID. The ID is not human-friendly, so the product's name is used the human-visible text instead of the ID.
<h1 itemscope> <data itemprop="product-id" value="9678AOU879">The Instigator 2000</data> </h1>
For numeric data, the meter element and its value attribute can be used instead.
Here a rating is given using a meter element.
<div itemscope itemtype="http://schema.org/Product">
<span itemprop="name">Panasonic White 60L Refrigerator</span>
<img src="panasonic-fridge-60l-white.jpg" alt="">
<div itemprop="aggregateRating"
itemscope itemtype="http://schema.org/AggregateRating">
<meter itemprop="ratingValue" min=0 value=3.5 max=5>Rated 3.5/5</meter>
(based on <span itemprop="reviewCount">11</span> customer reviews)
</div>
</div>
Similarly, for date- and time-related data, the time element and its datetime attribute can be used instead.
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.
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").
The type gives the context for the properties, thus selecting 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.
Several types can share a vocabulary. For example, the types "http://example.org/people/teacher" and "http://example.org/people/engineer" could be defined to use the same vocabulary
(though maybe some properties would not be especially useful in both cases, e.g. maybe the "http://example.org/people/engineer" type might not typically be used with the
"classroom" property). Multiple types defined to use the same vocabulary can
be given for a single item by listing the URLs as a space-separated list in the attribute' value.
An item cannot be given two types if they do not use the same vocabulary, however.
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.
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 |
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(s) 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 a particular 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 an 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].itemValue + '!');
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 all of 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.)
The microdata model consists of groups of name-value pairs known as items.
Each group is known as an item. Each item can have item types, a global identifier (if the vocabulary specified by the item types support global identifiers for 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). The names are unordered relative to each other, but if a particular name has multiple values, they do have a relative order.
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
types of the item.
The itemtype attribute, if specified, must have a value that
is an unordered set of unique space-separated tokens that are
case-sensitive, each of which is a valid URL that is an absolute
URL, and all of which are defined to use the same vocabulary. The attribute's value must
have at least one token.
The item types of an item are the tokens obtained
by splitting the element's itemtype attribute's value on spaces. If the itemtype attribute is missing or parsing it in this way finds no
tokens, the item is said to have no item types.
The item types must all be types defined in applicable specifications and must all be defined to use the same vocabulary.
Except if otherwise specified by that specification, the URLs given as the item types 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.
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 types for a typed item is the item's item types, if it has any, or else is the relevant types of the item for which it is a property's value.
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.
The exact meaning of a global identifier is determined by the vocabulary's specification. It is up to such specifications to define whether multiple items with the same global identifier (whether on the same page or on different pages) are allowed to exist, and what the processing rules for that vocabulary are with respect to handling the case of multiple items with the same ID.
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.
The itemref attribute is not part of the
microdata data model. It is merely a syntactic construct to aid authors in adding annotations to
pages where the data to be annotated does not follow a convenient tree structure. For example, it
allows authors to mark up data in a table so that each column defines a separate item, while keeping the properties in the cells.
This example shows a simple vocabulary used to describe the products of a model railway manufacturer. The vocabulary has just five property names:
This vocabulary has four defined item types:
Each item that uses this vocabulary can be given one or more of these types, depending on what the product is.
Thus, a locomotive might be marked up as:
<dl itemscope itemtype="http://md.example.com/loco
http://md.example.com/lighting">
<dt>Name:
<dd itemprop="name">Tank Locomotive (DB 80)
<dt>Product code:
<dd itemprop="product-code">33041
<dt>Scale:
<dd itemprop="scale">HO
<dt>Digital:
<dd itemprop="digital">Delta
</dl>
A turnout lantern retrofit kit might be marked up as:
<dl itemscope itemtype="http://md.example.com/track
http://md.example.com/lighting">
<dt>Name:
<dd itemprop="name">Turnout Lantern Kit
<dt>Product code:
<dd itemprop="product-code">74470
<dt>Purpose:
<dd>For retrofitting 2 <span itemprop="track-type">C</span> Track
turnouts. <meta itemprop="scale" content="HO">
</dl>
A passenger car with no lighting might be marked up as:
<dl itemscope itemtype="http://md.example.com/passengers"> <dt>Name: <dd itemprop="name">Express Train Passenger Car (DB Am 203) <dt>Product code: <dd itemprop="product-code">8710 <dt>Scale: <dd itemprop="scale">Z </dl>
Great care is necessary when creating new vocabularies. Often, a hierarchical approach to types can be taken that results in a vocabulary where each item only ever has a single type, which is generally much simpler to manage.
itemprop attributeEvery HTML element may have an itemprop attribute specified, if doing so adds one or more properties 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 must ensure all such property names contain no "." (U+002E) characters, no ":" (U+003A) 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 id="x"> <p itemprop="a">1</p> </div> <div itemscope itemref="x"> <p itemprop="b">test</p> <p itemprop="a">2</p> </div>
The property value of a name-value pair added by an
element with an itemprop attribute is as given for the first
matching case in the following list:
itemscope attributeThe value is the item created by the element.
meta elementThe value is the value of the element's content attribute,
if any, or the empty string if there is no such attribute.
audio, embed, iframe,
img, source, track, or video elementThe 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.
a, area, or link elementThe 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.
object elementThe 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.
data elementThe value is the value of the element's value attribute,
if it has one, or the empty string otherwise.
meter elementThe value is the value of the element's value attribute,
if it has one, or the empty string otherwise.
time elementThe value is the element's datetime value.
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, as defined by the property's definition, is an absolute URL, the property must be specified using a URL property element.
These requirements do not apply just because a property value happens to match the syntax for a URL. They only apply if the property is explicitly defined as taking such a value.
For example, a book about the first moon landing could be
called "mission:moon". A "title" property from a vocabulary that defines a title as being a string
would not expect the title to be given in an a element, even though it looks like a
URL. On the other hand, if there was a (rather narrowly scoped!) vocabulary for
"books whose titles look like URLs" which had a "title" property defined to take a URL, then the
property would expect the title to be given in an a element (or one of the
other URL property elements), because of the requirement above.
To find the properties of an item defined by the element root, the user agent must run the following steps. These steps are also used to flag microdata errors.
Let results, memory, and pending be empty lists of elements.
Add the element root to memory.
Add the child elements of root, if any, to pending.
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.
Loop: If pending is empty, jump to the step labeled end of loop.
Remove an element from pending and let current be that element.
If current is already in memory, there is a microdata error; return to the step labeled loop.
Add current to memory.
If current does not have an itemscope attribute, then: add all the child elements of current to pending.
If current has an itemprop
attribute specified and has one or more property names, then add current to results.
Return to the step labeled loop.
End of loop: Sort results in tree order.
Return results.
A document must not contain any items for which the algorithm to find the properties of an item finds any microdata errors.
An item is a top-level
microdata item if its element does not have an itemprop
attribute.
All itemref attributes in a Document must be
such that there are no cycles in the graph formed from representing each item in the Document as a node in the graph and each
property of an item whose value is another item as an edge in the graph connecting
those two 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.
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:
images/house.jpeg
http://www.opensource.org/licenses/mit-license.php
...and one with:
images/mailbox.jpeg
http://www.opensource.org/licenses/mit-license.php
Currently, the itemscope, itemprop, and other microdata attributes are only defined for
HTML elements. This means that attributes with the literal names "itemscope", "itemprop", etc, do not cause microdata
processing to occur on elements in other namespaces, such as SVG.
Thus, in the following example there is only one item, not two.
<p itemscope></p> <!-- this is an item (with no properties and no type) -->
<svg itemscope></svg> <!-- this is not, it's just an svg element with an invalid unknown attribute -->
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 the types given in the argument, if any are
listed.
The types argument is interpreted as a space-separated list of types.
propertiesIf the element has an itemscope attribute, returns an
HTMLPropertiesCollection object with all the element's properties. Otherwise, an
empty HTMLPropertiesCollection object.
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 InvalidAccessError exception.
The document.getItems(typeNames) method takes a 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 whose types include all the
types specified in the method's argument, having obtained the types by splitting the string on spaces. If there are no tokens specified in the
argument, 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. 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 element's
root element (which element this is might change during the collection's lifetime, as
the element moves between different subtrees), whose filter matches only elements that 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:
itemprop attributeThe attribute must return null on getting and must throw an
InvalidAccessError exception on setting.
itemscope attributeThe attribute must return the element itself on getting and must throw an
InvalidAccessError exception on setting.
meta elementThe attribute must act as it would if it was reflecting the
element's content content attribute.
audio, embed, iframe,
img, source, track, or video elementThe attribute must act as it would if it was reflecting the
element's src content attribute.
a, area, or link elementThe attribute must act as it would if it was reflecting the
element's href content attribute.
object elementThe attribute must act as it would if it was reflecting the
element's data content attribute.
data elementThe attribute must act as it would if it was reflecting the
element's value content attribute.
meter elementThe attribute must act as it would if it was reflecting the
element's value content attribute.
time elementOn getting, if the element has a datetime content
attribute, the IDL attribute must return that content attribute's value; otherwise, it must
return the element's textContent. On setting, the IDL attribute must act as it would
if it was reflecting the element's datetime content attribute.
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]));
The HTMLPropertiesCollection interface is used for collections of
elements that add name-value pairs to a particular
item in the microdata model.
interface HTMLPropertiesCollection : HTMLCollection {
// inherits length and item()
getter PropertyNodeList? namedItem(DOMString name); // shadows inherited namedItem()
readonly attribute DOMString[] names;
};
typedef sequence<any> PropertyValueArray;
interface PropertyNodeList : NodeList {
PropertyValueArray getValues();
};
lengthReturns the number of elements in the collection.
item(index)Returns the element with index index from the collection. The items are sorted in tree order.
namedItem(name)Returns a PropertyNodeList object containing any elements that add a property named name.
Returns a PropertyNodeList object containing any elements that add a property named name. The name index has to be one of the values listed in the names list.
namesReturns an array with the property names of the elements in the collection.
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, in tree order, ignoring later duplicates.
The names attribute must
return a live read only array 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 IDL attribute of each of the
elements represented by the object, in tree order.
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:
Let result be an empty object.
Let items be an empty array.
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.
Add an entry to result called "items" whose
value is the array items.
Return the result of serializing result to JSON in the shortest
possible way (meaning no whitespace between tokens, no unnecessary zero digits in numbers, and
only using Unicode escapes in strings for characters that do not have a dedicated escape
sequence), and with a lowercase "e" used, when appropriate, in the
representation of any numbers. [JSON]
This algorithm returns an object with a single property that is an array, instead of just returning an array, so that it is possible to extend the algorithm in the future if necessary.
When the user agent is to get the object for an item item, optionally with a list of elements memory, it must run the following substeps:
Let result be an empty object.
If no memory was passed to the algorithm, let memory be an empty list.
Add item to memory.
If the item has any item types, add an entry to result called "type" whose value is an array listing the
item types of item, in the order they were specified on the
itemtype attribute.
If the item has a global identifier, add an entry to result called "id" whose value is the global
identifier of item.
Let properties be an empty object.
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:
Let value be the property value of element.
If value is an item, then: If value is in memory, then let value be
the string "ERROR". Otherwise, get the object for value, passing a copy of memory, and then replace value with the object returned from those steps.
For each name name in element's property names, run the following substeps:
If there is no entry named name in properties, then add an entry named name to properties whose value is an empty array.
Append value to the entry named name in properties.
Add an entry to result called "properties" whose
value is the object properties.
Return result.
For example, take this markup:
<!DOCTYPE HTML>
<title>My Blog</title>
<article itemscope itemtype="http://schema.org/BlogPosting">
<header>
<h1 itemprop="headline">Progress report</h1>
<p><time itemprop="datePublished" datetime="2013-08-29">today</time></p>
<link itemprop="url" href="?comments=0">
</header>
<p>All in all, he's doing well with his swim lessons. The biggest thing was he had trouble
putting his head in, but we got it down.</p>
<section>
<h1>Comments</h1>
<article itemprop="comment" itemscope itemtype="http://schema.org/UserComments" id="c1">
<link itemprop="url" href="#c1">
<footer>
<p>Posted by: <span itemprop="creator" itemscope itemtype="http://schema.org/Person">
<span itemprop="name">Greg</span>
</span></p>
<p><time itemprop="commentTime" datetime="2013-08-29">15 minutes ago</time></p>
</footer>
<p>Ha!</p>
</article>
<article itemprop="comment" itemscope itemtype="http://schema.org/UserComments" id="c2">
<link itemprop="url" href="#c2">
<footer>
<p>Posted by: <span itemprop="creator" itemscope itemtype="http://schema.org/Person">
<span itemprop="name">Charlotte</span>
</span></p>
<p><time itemprop="commentTime" datetime="2013-08-29">5 minutes ago</time></p>
</footer>
<p>When you say "we got it down"...</p>
</article>
</section>
</article>
It would be turned into the following JSON by the algorithm above (supposing that the page's
URL was http://blog.example.com/progress-report):
{
"items": [
{
"type": [ "http://schema.org/BlogPosting" ],
"properties": {
"headline": [ "Progress report" ],
"datePublished": [ "2013-08-29" ],
"url": [ "http://blog.example.com/progress-report?comments=0" ],
"comment": [
{
"type": [ "http://schema.org/UserComments" ],
"properties": {
"url": [ "http://blog.example.com/progress-report#c1" ],
"creator": [
{
"type": [ "http://schema.org/Person" ],
"properties": {
"name": [ "Greg" ]
}
}
],
"commentTime": [ "2013-08-29" ]
}
},
{
"type": [ "http://schema.org/UserComments" ],
"properties": {
"url": [ "http://blog.example.com/progress-report#c2" ],
"creator": [
{
"type": [ "http://schema.org/Person" ],
"properties": {
"name": [ "Charlotte" ]
}
}
],
"commentTime": [ "2013-08-29" ]
}
}
]
}
}
]
}
If the itemprop attribute is
present on link or meta, they are
flow content and phrasing content. The
link and meta elements may be used where
phrasing content is expected if the itemprop attribute is present.
If a link element has an itemprop attribute, the rel attribute may be omitted.
If a meta element has an itemprop attribute, the name, http-equiv, and charset attributes must be omitted,
and the content attribute
must be present.
If the itemprop is specified
on an a or area element, then the href attribute must also be
specified.
If the itemprop is specified
on an iframe element, then the data attribute must also be
specified.
If the itemprop is specified
on an embed element, then the data attribute must also be
specified.
If the itemprop is specified
on an object element, then the data attribute must also be
specified.
If the itemprop is specified
on a media element, then the src attribute must also be
specified.
The drag-and-drop initialization steps are:
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.
application/microdata+jsonThis registration is for community review and will be submitted to the IESG for review, approval, and registration with IANA.
application/json [JSON]application/json [JSON]application/json [JSON]application/json [JSON]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. Thus, the relevant specifications
are the JSON specification and this specification. [JSON]
Applications that transfer data intended for use with HTML's microdata feature, especially in the context of drag-and-drop, are the primary application class for this type.
application/json [JSON]application/json [JSON]application/json [JSON]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]
All references are normative unless marked "Non-normative".
XMLHttpRequest, A. van Kesteren. WHATWG.