Ahoy,

I would like to contribute to this thread by explaining a problem that occurs often in telecommunications and logistics.

It is common to have planning tools that allow the user to 'fork' the master view of the 'domain model' and make local changes to 
explore "what ifs". Alas. the domain model is a directed graph of many thousands of instances, born of hundreds of classes, so 
duplicating all of this is not feasible.

I have always wanted an object mechanism to detect 'copy of write', so that I might slay this pesky problem. If I had "OCOW"
(Object Copy on Write), I could let the happy users work on the master object graph and manage the small portion that was changed 
by an such user experimentation. Obviously, there would need to be a nice exceptions or dependencies to wrap all this.


My question (I really do not know) then is: does immutability, as proposed in this thread, help ?

Brent