[Editor's Note: In our most recent SemanticLink podcast with special guest R.V. Guha, we mentioned RDFa 1.1 Lite, proposed by Ben Adida at last month's Schema.org workshop. Thanks to Manu Sporny for sharing the following look at RDFa 1.1 Lite.]

Summary: RDFa 1.1 Lite is a simple subset of RDFa consisting of the following attributes: vocab, typeof, property, rel, about and prefix.

During the schema.org workshop, a proposal was put forth by RDFa’s resident hero, Ben Adida, for a stripped down version of RDFa 1.1, called RDFa 1.1 Lite. The RDFa syntax is often criticized as having too much functionality, leaving first-time authors confused about the more advanced features. This lighter version of RDFa will help authors easily jump into the Linked Data world. The goal was to create a very minimal subset that will work for 80% of the folks out there doing simple markup for things like search engines.

vocab, typeof and property

RDFa, like Microformats and Microdata, allow us to talk about things on the Web. 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 Web 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 1-800-555-0155.
</p>

As you will note above, we have specified that we’re going to be using the vocabulary that can be found at the http://schema.org/ Web address. This is a vocabulary that has been released by Google, Microsoft and Yahoo! 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’re talking about a Person.

<p vocab="http://schema.org/" typeof="Person">
   My name is Manu Sporny and you can give me a ring via 1-800-555-0155.
</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 and phone number:

<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">1-800-555-0155</span>.
</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.

rel

At times, two things on the Web may be related to one another in a specific way. For example, the current page may describe a thing that has a picture of it somewhere else on the Web.

<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">1-800-555-0155</span>.
   <img rel="image" src="http://manu.sporny.org/images/manu.png" />
</p>

The example above links the Person on the page to the image elsewhere on the Web using the “image” relationship. A search engine will now be able to divine that the Person on the page is depicted by the image that is linked to in the page.

about

If you want people to link to things on your page, you can identify the thing using a hash and a name. For example:

<p vocab="http://schema.org/" about="#manu" typeof="Person">
   My name is
   <span property="name">Manu Sporny</span>
   and you can give me a ring via
   <span property="telephone">1-800-555-0155</span>.
   <img rel="image" src="http://manu.sporny.org/images/manu.png" />
</p>

So, 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 about attribute. Therefore, the identifier for the thing on the page would be: http://example.org/people#manu. This feature is similar to, but not exactly like, the id attribute in HTML.

prefix

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 blog, we could do something like the following:

<p vocab="http://schema.org/" prefix="foaf: http://xmlns.com/foaf/0.1/"
      about="#manu" typeof="Person">
   My name is
   <span property="name">Manu Sporny</span>
   and you can give me a ring via
   <span property="telephone">1-800-555-0155</span>.
   <img rel="image" src="http://manu.sporny.org/images/manu.png" />
   I have a <a rel="foaf:weblog" href="http://manu.sporny.org/">blog</a>.
</p>

The example assigns a short-hand prefix to the Friend-of-a-Friend vocabulary, foaf, and uses that prefix to specify the weblog vocabulary term. Since schema.org doesn’t have a clear way of expressing a person’s blog location, we can depend on FOAF to get the job done.

One of the other nice things about RDFa 1.1 (and RDFa 1.1 Lite) is that a number of useful and popular prefixes are pre-defined, so you can skip declaring them altogether and just use the prefixes.

Simplicity

That’s it – that is RDFa 1.1 Lite. It consists of six simple attributes; vocab, typeof, property, rel, about, and prefix. RDFa 1.1 Lite is completely upwards compatible with the full set of RDFa 1.1 attributes.

The Others

The RDFa 1.1 attributes that have been left out of RDFa 1.1 Lite are: content, datatype, resource, and rev. The great thing about RDFa 1.1 Lite and RDFa 1.1 is that you can always choose to use one or more of those advanced attributes and a conformant RDFa 1.1 processor will always pick up on the advanced attributes. That means that you don’t have to do anything to switch back and forth between RDFa 1.1 Lite and the full version of RDFa 1.1