title: Why does Google Testing Tool use the "id" attribute to generate a URL for the Microdata item?
body: <p>I'm using some Microdata to describe a blog post, and I'm surprised by the value return for Schema.org’s <code>BlogPosting</code> by the Google Developers Testing Tool. </p>
  
  <p>I would have expected it to be the itemprop <code>url</code>, not a merge of the website URL and the item <code>id</code>.<br>
  Am I doing something wrong, or is it only a Google display issue?</p>
  
  <pre class="lang-html prettyprint-override"><code>&lt;div itemscope="itemscope"
       itemprop="blogPost"
       itemtype="http://schema.org/BlogPosting"
       id="foobar"&gt;
    &lt;a itemprop="url" href="/realone"&gt;real&lt;/a&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>Value returned by <a href="https://developers.google.com/structured-data/testing-tool/">https://developers.google.com/structured-data/testing-tool/</a>:</p>
  
  <pre class="lang-none prettyprint-override"><code>  BlogPosting:    http://www.example.com/foobar
    url:            http://www.example.com/realone
  </code></pre>