What's the difference between getting an managed object with
- (NSManagedObject *)objectRegisteredForID:(NSManagedObjectID *)objectID
and
- (NSManagedObject *)existingObjectWithID:(NSManagedObjectID *)objectIDerror:(NSError **)error
Are there different types of NSManagedObjectID? Is there a difference between a "registered ID" and an "non-registered ID"?