A Pelican at Blandings:

The individual or group credited with creating the main content of a product, such as a book, film, or other creative work. The value is a free‑text string representing the name(s) of the primary creator.

The physical form in which a book is published, such as paperback, hardcover, audio CD, or board book. It indicates the binding style and overall durability of the product.

The name of the entity that publishes or distributes the product, such as a book, magazine, or other media item.