In PTC Windchill Prediction I used the Import Wizard to import an EXCEL BOM. This works and the tool generates a "System Tree Identifier" column. Now I want to update the BOM also using the Import Wizard and an updated EXCEL BOM. I selected "I want to update records" in the wizard but I got an error message "For an update, you must import the Identifier field". I don't know how to do this, my EXCEL BOM does not contain such an Identifier like the System Tree Identifier in the Tool. Should/can I define e.g. the Reference Designator of the parts as Identifier?