While RWStringID can help alleviate identification collisions, the possibility of collisions between RWStringIDs of different classes still exists. Collisions can occur:

In some cases, collisions like these will be unimportant. Automatically generated RWClassIDs are guaranteed to be distinct from one another and from any legal user-provided RWClassID. The virtual isA() method, the stringID() method, and constructor lookup based on the RWClassID will all continue to work correctly.

There will be some situations, however, where collisions will cause difficulty. Polymorphic persistence of classes with user-chosen RWStringIDs that collide will not work correctly. In these cases, the data will not be recoverable, even though it is stored correctly. Similarly, user code that depends on distinguishing between classes based only on their RWStringIDs will fail.

As a developer, you can work to avoid such collisions. First of all, you should use an RWStringID which is unlikely to collide with any other. For instance, you might choose RWStringIDs that mimic the inheritance hierarchy of your class, or that imbed your name, your company's name, a creation time, or a file path such as found in revision control systems. And of course, you should always test your program to insure that the class actually associated with your RWStringID is the one you expected.