HTML5: Up and Running

The Microdata Data Model

Defining your own microdata vocabulary is easy. First you need a namespace, which is just a URL. The namespace URL can point to a working web page, although that’s not strictly required. Let’s say I want to create a microdata vocabulary that describes a person. If I own the data-vocabulary.org domain, I’ll use the URL http://data-vocabulary.org/Person as the namespace for my microdata vocabulary. That’s an easy way to create a globally unique identifier: pick a URL on a domain that you control.

In this vocabulary, I need to define some named properties. Let’s start with three basic properties:

• name (the user’s full name)

• photo (a link to a picture of the user)

• url (a link to a site associated with the user, like a blog or a Google profile)

Two of these properties are URLs, and the other is plain text. Each of them lends itself to a natural form of markup, even before you start thinking about microdata or vocabularies. Imagine that you have a profile page or an “about” page. Your name is probably marked up as a heading, like an <h1> element. Your photo is probably an <img> element, since you want people to see it. And any URLs associated with your profile are probably already marked up as hyperlinks, because you want people to be able to click them. For the sake of discussion, let’s say your entire profile is also wrapped in a <section> element to separate it from the rest of the page content. Thus:

<section> <h1>Mark Pilgrim</h1> <p><img src="http://www.example.com/photo.jpg" ...