describe differences from the book

README

@@ -1,9 +1,12 @@
 This project contains the depot application as described in the Agile Development with Rails book from the
 Pragmatic Programmers (http://pragprog.com/titles/rails3/agile-web-development-with-rails-third-edition).
 
-It has been modified to use HAML (http://haml-lang.com/) & SASS (http://sass-lang.com/) for HTML & CSS generation.
+Departures from the book:
 
-In addition the user, product and store controllers have been modified to use the POST-REDIRECT-GET web application
-design pattern (http://en.wikipedia.org/wiki/Post/Redirect/Get) as an exercise to see what it takes to make
-active-resource controllers behave nicely with browsers.
+1. All model objects use a UUID as their primary key, rather than the standard Rails autogenerated numeric key.
 
+2. Uses HAML (http://haml-lang.com/) and SASS (http://sass-lang.com/) for HTML & CSS generation.
+
+3. The user, product and store controllers have been modified to use the POST-REDIRECT-GET web application
+   design pattern (http://en.wikipedia.org/wiki/Post/Redirect/Get) as an exercise to see what it takes to make
+   active-resource controllers (and other rails controllers) behave nicely with browsers' back & refresh buttons.