title: How does Yelp create the "Review Highlights" section?
body: <p>Take the following link as an example: <a href="http://www.yelp.com/biz/chef-yu-new-york" rel="nofollow">http://www.yelp.com/biz/chef-yu-new-york</a>.</p>
  
  <p>In the section called 'Review Highlights', there are 3 phrases (spicy diced chicken, happy hour, lunch specials) that are highlighted based on reviews submitted by users. Obviously, these are the phrases that appeared most often, or longest phrases that appeared often, or some other logic. </p>
  
  <p>Their official explanation is this:</p>
  
  <blockquote>
    <p>In their reviews, Yelpers mentioned the linked phrases below a lot.
    And these aren't any old common phrases, they're also the ones that
    our Yelp Robots have determined are unique and good, quick ways to
    describe this business. Click any of the phrases to see all the
    reviews that mention it.</p>
  </blockquote>
  
  <p>My question is, what did they use to mine the text input to get these data points? Is it some algorithm based on Lempel Ziv, or some kind of map reduce? I was not a CS major, so probably am missing something foundational here. Would love some help, theories, etc. </p>
  
  <p>Thanks!</p>