Chapter 2 - defining nonfunctional requirements

The authors define a functional requirement as "the functionality that the application must offer", and the nonfunctional requirements as everything else you need to do. Right off the bat, I struggle with this definition! They give performance as an example of a nonfunctional requirement, but obviously that's a matter of degree. Let's see if they clarify, or just allow the definition to be very fuzzy at the edges. Twitter example They start off with a motivating example, of a common interview question: let's design a service like twitter. Given three tables: users id screen_name profile_image 12 jack 123.png posts id sender_id fk(users) timestamp text 20 12 123456 just setting up my twttr follows follower_id fk(users) followee_id fk(users) 9923882 12 They give the first pass SQL query to create a timeline page: SELECT posts.*, users.* FROM posts JOIN follows ON posts.sender_id = follows.followee_id JOIN users ON posts.sender_id = users.id ORDER BY posts.timestamp DESC LIMIT 1000 This…