RIP database ER-Diagram III : object versioning

                                              
 +-------------+         +-------------+      
 | last        |         | serials     |      
 +-------------+       1 +-------------+      
 | serial      |   1 +-}-o serial      |  1   
 | prev_serial o---}-+   | prev_serial o--}-+ 
 | object      |     |   | object      |    | 
 +-------------+     |   +-------------+    | 
                     |                      | 
                     +----------------------+