It doesn't give out ratings. It will rather generate tags and categories which represent a submission. Tags such as: erlang, database, module, in-memory, etc. You can also generate other features such as word count, presence of images, (domain name, poster's name, etc.)<p>Now what you do is to go through all (or as many as you could) stories that have been on HN front page, calculate features for those stories. Those features are used to learn a prediction model which you can apply to new stories to predict ratings.