title: Offer (with priceSpecification) nested within Product throws Warning
body: <p>Nesting an Offer that has a priceSpecification inside a Product throws up an <em>Incomplete microdata</em> warning in Google Rich Snippets testing tool. </p>
  
  <p>This</p>
  
  <pre><code>&lt;div itemscope itemtype="http://schema.org/Product"&gt;
      &lt;h1 itemprop="name"&gt;1984 Vintage Selection Cabernet Sauvignon&lt;/h1&gt;
      &lt;p itemprop="description"&gt;Cabernet Sauvignon.&lt;/p&gt;
      &lt;div itemprop="offers" itemscope itemtype="http://schema.org/Offer"&gt;
          &lt;p itemprop="priceSpecification" itemscope itemtype="http://schema.org/priceSpecification"&gt;Prices start at 
          &lt;meta itemprop="priceCurrency" content="GBP" /&gt;£&lt;span itemprop="price"&gt;0.71&lt;/span&gt; (per bottle)&lt;/p&gt;
          &lt;meta itemprop="validThrough" content="2013-09-01" /&gt;
      &lt;/div&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>throws the following warning in google rich snippets testing tool:
  <em>Warning: Incomplete microdata with schema.org.</em></p>
  
  <p>If I move Offer outside Product:</p>
  
  <pre><code>&lt;div itemscope itemtype="http://schema.org/Product"&gt;
      &lt;h1 itemprop="name"&gt;1984 Vintage Selection Cabernet Sauvignon&lt;/h1&gt;
      &lt;p itemprop="description"&gt;Cabernet Sauvignon.&lt;/p&gt;
  &lt;/div&gt;
  &lt;div itemprop="offers" itemscope itemtype="http://schema.org/Offer"&gt;
      &lt;p itemprop="priceSpecification" itemscope itemtype="http://schema.org/priceSpecification"&gt;Prices start at 
      &lt;meta itemprop="priceCurrency" content="GBP" /&gt;£&lt;span itemprop="price"&gt;0.71&lt;/span&gt; (per bottle)&lt;/p&gt;
      &lt;meta itemprop="validThrough" content="2013-09-01" /&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>then the warning is no longer thrown up, but this doesn't appear to make sense, as the Offer is not linked to the Product it's applicable to.</p>
  
  <p>All the examples at schema.org nest Offer within Product, however, none of them use priceSpecification. I could only find one blog post where Offer is not nested within Product: <a href="http://seolobster.de/richsnippets-schema-org-products-update" rel="nofollow">http://seolobster.de/richsnippets-schema-org-products-update</a>. This does not fill me with confidence to use in a live environment.</p>
  
  <p>Which is correct? Especially if you throw in more than one Offer?</p>