For my scenario, it related to SharePoint, where I am trying to create 2 or more items from 1 form (the master and detail). Where SharePoint does not issue an ID to the master item until it has been submitted, and therefore, it is impossible to issue that same parent ID to the detail items until the item has been created. Therefore, we need to create our own ID, and a GUID is the most logical way of doing this.
We now have a GUID function that can create new GUIDs.
Check out the GUID function's documentation and the blog post on using GUIDs with CDS and SQL Server.