Google Search Engine Adds Support for RDFa, Or Do They?

Via a post and an interview on the O’Reilly Radar blog, Google announced limited support for parsing RDFa statements and microformat properties in web page HTML coding and using those statements to enhance the relevance of search results as so-called “rich snippets”. In looking at the example review markup outlined in the O’Reilly post, though, I was struck by some unusual and unexpected markup. Specifically, that the namespace was this http://rdf.data-vocabulary.org/ thing that I had never seen before, and the “rating” property didn’t have any corresponding range that would make that numeric value useful in a computational sense.

<div xmlns:v=”http://rdf.data-vocabulary.org” typeof=”v:review”>
<div>
79 of 98 people found the following review helpful:
</div>

<div>
<span><span property=”v:rating”>5.0</span> out of 5 stars</span>
<span><b>American Biographer: Jon Meacham</b>/span>
</div>

<div><a href=”http://www.amazon.com/gp/pdp/profile/A2G8PQ9HNUY6NA/”>
<span property=”v:reviewer”
about=”http://www.amazon.com/gp/pdp/profile/A2G8PQ9HNUY6NA/”>Marian the Librarian</span></a> (NY, NY) –
<span property=”v:dtreviewed”>1st April 2009</span>
</div>

<div>
<b>This review is from:
<a property=”v:itemreviewed”
about=”http://www.amazon.com/American-Lion-Andrew-Jackson-White/dp/1400063256/”
href=”http://www.amazon.com/American-Lion-Andrew-Jackson-White/dp/1400063256/”>
American Lion: Andrew Jackson in the White House (Hardcover)</a></b>

</div>
<div class=”review” property=”v:description”>
American Lion is a wonderfully crafted biography about an incredibly interesting
and oft-overlooked American who helped shaped this country…
</div>
</div>

I didn’t think much of it, but this evening I came across a post by Ian Davis that confirmed my odd feelings:

However, a closer look reveals that Google have basically missed the point of RDFa. The RDFa support is limited to the properties and classes defined on a hastily thrown together site called data-vocabulary.org. There you will find classes for Person and Organization and properties for names and addresses, completely ignoring the millions of pieces of data using well established terms from FOAF and the like.

That’s when I figured out why the rating property looked weird. Rather than using the http://vocab.org/review/review.rdf vocabulary, which defines a http://purl.org/stuff/rev#minRating and a http://purl.org/stuff/rev#minRating, the geeks at Google invented something new. Ian’s post goes into greater detail about why this goes against the typical trend of reusing vocabularies. I share Ian’s hope that this is an error that will be corrected shortly, and his fear that this could be an example of a market leader trying to bend the rest of the world to its own ways.

Update


13-May-2009: For those seeking more information, there is a detailed posting on the Google Webmaster Central Blog on the Rich Snippets. And the question of the day seems to be whether Google will support vocabularies other than their own.

The text was modified to update a link from http://vocab.org/review/review.rdf to http://vocab.org/review/terms.html on January 28th, 2011.

(This post was updated on 27-Jan-2011.)