SKU for APP

The Wikipedia explains that:

It is a unique identifier for each distinct product and service that can be purchased. The usage of SKU is rooted in data management, enabling the company to systematically track its inventory or product availability, such as in warehouses and retail outlets. They are often assigned and serialized at the merchant level. Each SKU is attached to an item, variant, product line, bundle, service, fee, or attachment

For our App SKU, just use <com>.<company name>.<product>, it's a little like program namespace.