ID

The Unique ID will just be a number starting at 0. Gaps will occur if items are removed from the data store. Any such gaps must be handled in such a way that iteration using something like a for loop would not encounter them. How this is done is up to the implementation.

One such way would be to fill gaps with ``blank'' DataItems which would also be in an internal list of unallocated items. When a new item is added to the data store rather than creating the DataItem at $max+1$ it would just pick the first one from the list of gaps.

This way a remove would generate a gap and an add would remove it:

Items:	0	1	2	3	4
Start	allocated	allocated	allocated	allocated	allocated
Remove Item 2	allocated	allocated	unallocated	allocated	allocated
Remove item 0	unallocated	allocated	unallocated	allocated	allocated
Add new item	allocated	allocated	unallocated	allocated	allocated
Add new item	allocated	allocated	allocated	allocated	allocated