Search engine giants Google, Yahoo and Microsoft (Bing) today announced schema.org, a new initiative to create and support a common vocabulary for structured data markup on web pages.

Schema.org has been developed in an effort to held site owners and developers learn about structured data and improve how their sites appear in major search engines. The site aims to be a one stop resource for webmasters looking to add markup to their pages.

Search engines have been working independently to support structured markup for a few years now. Google introduced rich snippets to Google search in 2009 to help people find better summaries of reviews and people, and since that time they've expanded to new kinds of rich snippets, including recipes and events.

"We want to continue making the open web richer and more useful," said Ramanathan Guha, Google Fellow. "We know that it takes time and effort for webmasters to add this markup to their pages, and adding markup is much harder if every search engine asks for data in a different way. That's why we've come together with other search engines to support a common set of schemas, just as we came together to support a common standard for sitemaps in 2006. With schema.org, site owners can improve how their sites appear in search results not only on Google, but on Bing, Yahoo! and potentially other search engines as well in the future," he added.

In addition to consolidating the schemas for the categories we already support, schema.org also introduces schemas fornew categories, including movies, music, organizations, TV shows, products, places and more.