+---------+      +----------+     +--------+        
|  dogs   |      |replica 1 |     |   a    |        
|         |      |          |     |        |        
+---------+      +----------+     +--------+        
   |                ^                |              
   |                |                |              
 chase              | To err is human, to moo bovine
   |                |                |  *           
   v                v                v              
+---------+       +----------+     +--------+       
|  cats   |       |replica 2 |     |   b    |       
|         |       |          |     |        |       
+---------+       +----------+     +--------+       
   |                                                
 chase                                              
   |                                                
   v                                                
+---------+                                         
|  mice   |                                         
|         |                                         
+---------+                                         
