The eBay produdt ID (ePID) or external IDs associated with the product. Use the Reference value as input to search for the same product in the future, or use the ISBN, EAN, or UPC value (if returned). The ISBN, EAN, and UPC values can also be useful as keys if your application is comparing products across different sites. Always returned when Product is returned.
See the Field Index to learn which calls use productIdentifier.
Indicates if a product is the top or main product in a family (Head) or a variant of the head product (Member). If a product is not part of a product family, it is also the Head.
Sometimes several versions (or editions) of a product may be available. All versions of the same product are considered to be part of the same product family. Some product families may contain only one product; others may contain many products.
The product is the the head of the product family.