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Dear all:
Apologies for the confusion - the main cause of the problem is that Google is also accepting properties from the Yahoo review vocabulary http://purl.org/stuff/rev# without telling us ;-)
And the min/max rating in that vocabulary is underspecified - I thought it indicates the range of existing ratings (e.g. from 3 to 5), but Google seems to use as the range of the possible ratings.

The unfortunate effect is that a 4.5 rating with min=4 and max=5 means that Google would display only 2.5 stars on a 5-star-scale, because 4.5 is in the middle between 4 and 5.

So the official recommendation from our side is now to NOT USE review:minRating and review:maxRating. Simply delete the two lines:

>        <div property="review:minRating" datatype="xsd:integer" content="4"></div> 
>        <div property="review:maxRating" datatype="xsd:integer" content="5"></div> 


The complete pattern is

> 
> <div xmlns:review="http://purl.org/stuff/rev#"
> 	  xmlns:v="http://rdf.data-vocabulary.org/#"
> 	  typeof="gr:Offering" about="#offer">
>    <div rel="review:hasReview v:hasReview">
>      <div typeof="v:Review-aggregate review:Review">
>        <div property="review:rating v:average" datatype="xsd:float" content="4"></div>
>        <div property="review:totalRatings v:count" datatype="xsd:integer" content="6"></div>
>      </div>
>    </div>
> </div>

Still, v:average seems to be the correct property instead of v:rating for Google. But we asked them for clarification. Our tests show that both seem to work.

Best

Martin Hepp


On Jun 23, 2011, at 3:22 PM, Martin Hepp wrote:

> Dear all:
> 
> I just spotted a severe bug in the Google recipe for reviews, given at [1]. Please fix this in your implementations asap, because otherwise, the snippet in the Google search results may show less stars  than it should.
> 
> Instead of v:rating for the average, use v:average. If you use v:rating for aggregate reviews, Google seems to divide it by the number of reviews, so you may get only one star even if your average is 4.4.
> 
> The following would be a correct review pattern that works with both Google and Yahoo in RDFa:
> 
> <div xmlns:review="http://purl.org/stuff/rev#"
> 	  xmlns:v="http://rdf.data-vocabulary.org/#"
> 	  typeof="gr:Offering" about="#offer">
>    <div rel="review:hasReview v:hasReview">
>      <div typeof="v:Review-aggregate review:Review">
>        <div property="review:rating v:average" datatype="xsd:float" content="4"></div>
>        <div property="review:minRating" datatype="xsd:integer" content="4"></div> 
>        <div property="review:maxRating" datatype="xsd:integer" content="5"></div> 
>        <div property="review:totalRatings v:count" datatype="xsd:integer" content="6"></div>
>      </div>
>    </div>
> </div>
> 
> I have already asked Google to fix this in their documentation.
> 
> So please fix it in your code asap. Thanks!
> 
> Best wishes
> 
> Martin Hepp
> 
> [1] http://www.google.com/support/webmasters/bin/answer.py?answer=186036
> 
> 
> 
> 
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