/*
         +--------------------------+ 
         | ISame                    |   
	     +--------------------------+
	     | boolean same(ISame that) |
	     +--------------------------+
                       |
                      / \
                      ---
                       |
              --------------------
              |                  |
	+--------------+    +--------------+
	| Book         |    | Song         |
    +--------------+    +--------------+
    | String title |    | String title | 
	| String author|    | int    time  |
	| int    year  |    +--------------+  
    +--------------+    
           
*/  

interface ISame{
  // is this object the same as the given one?  
  boolean same(ISame that); 
}