Schema Markup for Reviews

So – reviews are always a great thing.  Reviews that Google can recognize as reviews and ratings are even better – enter Schema.org markup for reviews.  By marking up ratings and reviews on your website – you’re ensuring that google understands that the content is a review and how many stars that review received.  Rating in numbers is key in this understanding – computers cant really take words like “love” and “excellent” and convert them into a number an algorithm can understand and then use that number to rank you against your competition.  So – Schema markup not only can define the text of a review – but it defines the number you’re ranked out of 5 stars.
Here is an example of marking up an individual review

<div itemprop="review" itemscope itemtype="http://schema.org/Review">
    <span itemprop="name">Not a happy camper</span> -
    by <span itemprop="author">Ellie</span>,
    <meta itemprop="datePublished" content="2011-04-01">April 1, 2011
    <div itemprop="reviewRating" itemscope itemtype="http://schema.org/Rating">
      <meta itemprop="worstRating" content = "1">
      <span itemprop="ratingValue">1</span>/
      <span itemprop="bestRating">5</span>stars
    </div>
    <span itemprop="description">The lamp burned out and now I have to replace
    it. </span>
  </div>

http://ignitordigital.com/schema-markup-reviews-markup-monday/