Google, Bing and Yahoo may not be the best of friends, but every once in a while they do get together in a high-profile way.
Schema.org goes about this by offering new markup based on the W3C's draft HTML microdata specification, which in this case allows publishers to add data to their HTML tags to "help search engines better understand their websites".
There are specific types for different types of content, ranging from movies to restaurants. As an example, a movie type would augment standard HTML to help search engines understand the content:
<div itemscope itemtype ="http://schema.org/Movie">
<span>Director: <span itemprop="director">James Cameron</span> (born August 16, 1954)</span>
<span itemprop="genre">Science fiction</span>
<a href="../movies/avatar-theatrical-trailer.html" itemprop="trailer">Trailer</a>
It's not difficult to see why Google, Bing and Yahoo would like this microdata. Spidering the world's content and making sense of it all is really, really tough. Even with the best technology in the world, finding semantic meaning in huge amounts of semi-structured and unstructured information is challenging.
But publishers, lured by the promise that microdata could boost their position in the SERPs, can provide the desired semantic context manually. In other words, the major search engines can get publishers to do their work for them.
But should publishers go along? There are several big problems with Schema.org worth considering:
Adding the markup could be a lot of work.
Adding the Schema.org markup to existing content will require great effort for publishers with a lot of content. This will be especially true for publishers using content management systems, as many would need to update their templates and administrative interfaces to support Schema.org markup.
It can and will be abused.
Schema.org types may be more specific than meta tags which search engines largely ignore today, but just like meta tags, you can be sure SEO spammers and black hats will look to take advantage of them. In the worst case scenario, this would render Schema.org as worthless as meta tags for SEO purposes.
HTML is for display.
HTML describes how content should look when rendered; HTML is not designed to describe the content itself. That's one of the things XML is designed for.
The HTML microdata specification which Schema.org is based on may be a W3C draft, but that doesn't mean that there isn't a strong argument to be made that blurring the lines between HTML and XML is undesirable for just about everybody except search engines.
So should publishers completely ignore Schema.org? No. It will be interesting to see how Google, Bing and Yahoo use it in the next year, and what impact publishers who do adopt it see on their search rankings. In the meantime, most publishers should probably remain focused on the SEO basics.