Some RMI ID are assigned to the RMI functions which are in global{}. Of course, You can let some RMI functions have RMI IDs you want. Use the '[id=xxx]' phase like the below code.
global MedivalWorld 10000 { Foo([in] int x);// 10001 is assigned to ID automatically. [id=13000] id=Foo2([in] int y); // id is assigned to ID automatically. }