Integration can be at different application layers:

• Data Level Integration:
  
  
  1. Batch data transfer, OR
  
  
  2. On-line propagation of data updates
  
  
  3. 
     
  
  


• API Level Integration:
  
  
  1. Data is accessed through published API services
  
  


• Service Method Level Integration:
  
  
  1. Common services shared by different applications
  
  


• User Interface Level Integration:The controller reacts to the user input. It creates and sets the model.
  
  
  1. Common user interface (e.g. web based) for unified access to multiple applications.