anchor.diff:  
   ## Overview
   
  -This engine template provides personalized recommendation for e-commerce alike applications.
  -
  -The template has the following features:
  -
  -- handle out of stock items
  -- recommend items to new user who signs up after the model is trained.
  -- recommend unseen items only.
  +This engine template provides personalized recommendation for e-commerce applications with the following features by default:
  +
  +- Exclude out-of-stock items
  +- Provide recommendation to new users who sign up after the model is trained
  +- Recommend unseen items only
   
   WARNING: This template requires PredictionIO version >= 0.8.7
   
  
positive.code: }'
  ```
  
  Try to get recommendation for user *u1* again, you will see the unavaiable items (e.g. i4, i14, i11). won't be recommended anymore:
  
  ```
  curl -H "Content-Type: application/json" \
  
negative.code: 
  ## Collecting Data
  
  Next, let's collect training data for this Engine. By default,
  the E-Commerce Recommendation Engine Template supports 2 types of entities and 2 events: **user** and
  **item**; events **view** and **buy**. An item has the **categories** property, which is a list of category names (String). A user can view and buy an item.
  
  There is also one specical **constraint** entiy with entityId **unavailableItems**, which defines a list of unavailable items and is taken into account in realtime during serving.
  
  <%= partial 'shared/quickstart/install_sdk' %>
  
  