RDFa Lite is a minimal subset of RDFa, the Resource Description Framework in attributes, consisting of a few attributes that may be used to express machine-readable data in Web documents like HTML, SVG, and XML. While it is not a complete solution for advanced data markup tasks, it does work for most day-to-day needs and can be learned by most Web authors in a day.
This document is the culmination of a series of discussions between the World Wide Web Consortium, including the RDFa Working Group, the Vocabularies Community Group, the HTML Working Group, and the sponsors of the schema.org initiative, including Google, Yahoo!, Microsoft, and Yandex. It has received review from representatives in these organizations and enjoys consensus at this point in time. There were no changes made during the Proposed Recommendation period. The implementation report used by the director to transition to Recommendation has been made available.
The full RDFa syntax [[!rdfa-core]] provides a number of basic and advanced features that enable authors to express fairly complex structured data, such as relationships among people, places, and events in an HTML or XML document. Some of these advanced features may make it difficult for authors, who may not be experts in structured data, to use RDFa. This lighter version of RDFa is a gentler introduction to the world of structured data, intended for authors that want to express fairly simple data in their web pages. The goal is to provide a minimal subset that is easy to learn and will work for 80% of authors doing simple data markup.
RDFa Lite consists of five simple attributes;
prefix. RDFa 1.1 Lite is completely upwards compatible with the
full set of RDFa 1.1 attributes. This means that if an author finds that
RDFa Lite isn't powerful enough, transitioning to the full version of RDFa is
just a matter of adding the more powerful RDFa attributes into the existing
RDFa Lite markup.
RDFa, like Microformats [[microformats]] and Microdata [[microdata]], enables us to talk about things on the Web such that a machine can understand what we are saying. Typically when we talk about a thing, we use a particular vocabulary to talk about it. So, if you wanted to talk about People, the vocabulary that you would use would specify terms like name and telephone number. When we want to mark up things on the Web, we need to do something very similar, which is specify which vocabulary that we are going to be using. Here is a simple example that specifies a vocabulary that we intend to use to markup things in the paragraph:
<p vocab="http://schema.org/"> My name is Manu Sporny and you can give me a ring via 1-800-555-0199. </p>
In this example we have specified that we are going to be using the
vocabulary that can be found at
http://schema.org/. This is a vocabulary that has been
released by major search engine companies to talk about common things on the
Web that Search Engines care about – things like People, Places, Reviews,
Recipes, and Events. Once we have specified the vocabulary, we need to specify
the type of the thing that we're talking about. In this
particular case we are talking about a Person, which can be marked up like so:
<p vocab="http://schema.org/" typeof="Person"> My name is Manu Sporny and you can give me a ring via 1-800-555-0199. </p>
Now all we need to do is specify which properties of that person we want to point out to the search engine. In the following example, we mark up the person's name, phone number and web page. Both text and URLs can be marked up with RDFa Lite. In the following example, pay particular attention to the types of data that are being pointed out to the search engine, which are highlighted in blue:
<p vocab="http://schema.org/" typeof="Person"> My name is <span property="name">Manu Sporny</span> and you can give me a ring via <span property="telephone">1-800-555-0199</span> or visit <a property="url" href="http://manu.sporny.org/">my homepage</a>. </p>
Now, when somebody types in “phone number for Manu Sporny” into a search engine, the search engine can more reliably answer the question directly, or point the person searching to a more relevant Web page.
If you want Web authors to be able to talk about each thing on your
page, you need to create an identifier for each of these things. Just like we
create identifiers for parts of a page using the
in HTML, you can create identifiers for things described on a page using the
<p vocab="http://schema.org/" resource="#manu" typeof="Person"> My name is <span property="name">Manu Sporny</span> and you can give me a ring via <span property="telephone">1-800-555-0199</span>. <img property="image" src="http://manu.sporny.org/images/manu.png" /> </p>
If we assume that the markup above can be found at
http://example.org/people, then the identifier for the thing is
the address, plus the value in the
resource attribute. Therefore,
the identifier for the thing on the page would be:
http://example.org/people#manu. This identifier is also useful if
you want to talk about that same thing on another Web page. By identifying all
things on the Web using a unique Uniform Resource Locator (URL), we can start
building a Web of things. Companies building software for the Web can use this
Web of things to answer complex questions like: "What is Manu Sporny's phone
number and what does he look like?".
In some cases, a vocabulary may not have all of the terms an author needs when describing their thing. The last feature in RDFa 1.1 Lite that some authors might need is the ability to specify more than one vocabulary. For example, if we are describing a Person and we need to specify that they have a favorite animal, we could do something like the following:
<p vocab="http://schema.org/" prefix="ov: http://open.vocab.org/terms/" resource="#manu" typeof="Person"> My name is <span property="name">Manu Sporny</span> and you can give me a ring via <span property="telephone">1-800-555-0199</span>. <img property="image" src="http://manu.sporny.org/images/manu.png" /> My favorite animal is the <span property="ov:preferredAnimal">Liger</span>. </p>
The example assigns a short-hand prefix to the Open Vocabulary
ov) and uses that prefix to specify the
preferredAnimal vocabulary term. Since schema.org doesn't have
a clear way of expressing a favorite animal, the author instead depends on
this alternate vocabulary to get the job done.
RDFa 1.1 Lite also pre-defines a number of
useful and popular
prefixes, such as
schema. This ensures that even if authors forget to declare the
popular prefixes, that their structured data will continue to work. A full list
of pre-declared prefixes can be found in the
document for RDFa 1.1.
If you would like to learn more about what is possible with RDFa Lite, including an introduction to the data model, please read the section on RDFa Lite in the RDFa Primer [[rdfa-primer]].
In order for a document to be labeled as a conforming RDFa Lite 1.1 document:
prefix; it may also use
src, when the Host Language authorizes the usage of those attributes. However, even if authorized by the Host Language, the usage of
revSHOULD be restricted to non-RDFa usage patterns, as defined by the Host Language.
xmlnsattribute is not used to declare CURIE prefixes.
If additional non-RDFa Lite attributes are used from the RDFa Core 1.1 specification, the document MUST be referred to as a conforming RDFa 1.1 document. All conforming RDFa Lite 1.1 documents MAY be referred to as conforming RDFa 1.1 documents.
2014-12-16: Two grammatical errors have been changed in the Status Section
2014-12-16: References to the other RDFa documents have been updated
2014-12-16: The style of the references have been updated to the latest