title: Adhering to Google's Structured Data Policy
body: <p>Google's <a href="https://developers.google.com/search/docs/data-types/product" rel="nofollow noreferrer"><code>Product</code> structured data reference</a> recommends that <code>aggregateRating</code> be included. <a href="https://developers.google.com/search/docs/guides/prototype#common-sd-errors" rel="nofollow noreferrer">Common structured data errors</a> document says:</p>
  
  <blockquote>
    <p>The content referred to by the structured data is hidden from the user.</p>
  </blockquote>
  
  <p>My question is how to verify that Google understands my UI? I'm using (5) svg star images to indicate the rating but there's 3 flavors of star, empty, half and full. Do I need to add a <code>content="rating"</code> or <code>title="rating"</code> attribute or …? I'd like to understand how does Google know I'm showing the 5 stars at all? I could be using <code>.png</code> files, or unicode ★.</p>
  
  <pre class="lang-json prettyprint-override"><code>  "aggregateRating": {
      "@type": "AggregateRating",
      "ratingValue": "88",
      "bestRating": "100",
      "ratingCount": "20"
    }
  </code></pre>