title: Database / Schema structure to build a Wall system
body: <p>I've been doing some researches about how to build a wall system similar to FB in PHP.</p>
  
  <p>We planned to use an <strong>ODM</strong> (<a href="http://mandango.org" rel="nofollow">Mandango</a>, MongoDB) instead of a regular ORM (MySQL) to achieve this. Some friend told me about <em>inbox/outboxes</em> system.</p>
  
  <ul>
  <li><strong>Inbox</strong> are all the messages that friends posts to your wall</li>
  <li><strong>Outbox</strong> are all the message you post</li>
  </ul>
  
  <p>Why that ? Because it'll be simplier if you follow an user, you'll follow only his "<em>outbox</em>"</p>
  
  <p>Each time i'll post something to my wall, this message will be duplicated to each of my followers (which will generate a lot of data).
  But what about when a friend comments my post. On which entity is he going to comment my post ? Mine or his (because the content is duplicated) ?  </p>
  
  <p>What do you think ?
  Have you already thought of this kind of question ? Have you any answers ? 
  Thanks</p>