A Yelp user has a unique yelp ID$,$ first name, last name, gender, birthdate, birthplace, age, email, a profile picture, and list of friend ids. Yelp users can be complimented by their friends. A Yelp user can rate any business on a scale of $1-5$ and provide reviews. A user has an $"$ Activity Wall" where $10$ most recent Yelp reviews by user's friends are posted on the wall when the user $$follows$$ her friend$$s activities. In addition, the user can checkin to a particular business.