title: Is the MongooseJS "versionKey" (__v field) a "vector clock"?
body: <p>I've been using MongooseJS's <code>revisionKey</code> for a while now - the <code>__v</code> field that it includes with documents, by default. I understand what the purpose of the revision number is, and generally when it is updated.</p>
  
  <p>I was recently speaking with a friend about the idea of a "vector clock" and I mentioned MongoDB and MongooseJS having this <code>__v</code> field. At the time, it sounded like this could be a vector clock. But having read a little bit about vector clocks, now I'm not sure.</p>
  
  <p>So I'm wondering: Can the <code>versionKey</code> attribute of MongooseJS, and the <code>__v</code> field that it produces by default, be considered a vector clock? Yes, or no, and why?</p>