WorldShare Collection Manager
WorldCat knowledge base
If you choose select as the action column value, the system will try to select the title in the collection based on information in your KBART file. If it can't find the title, it will add the title as a new title in the collection.
If you choose overlay as the action column value, the system will try to select the title in the collection based on information in your KBART file AND set the customized information from your file (coverage, URL, staff notes, etc). If it can't find the title, it will add the title as a new title in the collection.
The difference between the two actions is that, when it's able to find the title, the select action selects the title as is, but overlay will both select the title and set your customized information. It's important to note that, for both of these actions, if the system can't find the title in the collection based on your KBART file information, it will add the title as a new title in the collection.