title: Strategy for sharing and reusing of schema parts in mongoose.js
body: <p>Suppose, I have two schemas, e.g. for <code>person</code> and <code>company</code>. Both of them should have an <code>address</code>, which consists of a <code>street name</code>, <code>number</code>, <code>zip</code> and <code>city</code>.</p>
  
  <p>What would be the strategy to avoid copying the <code>address</code> properties between the two schema definitions? I read about <a href="http://mongoosejs.com/docs/subdocs.html">sub docs</a>, but they seem to be (1) tied to exactly one parent schema, (2) always occur in an array.</p>