Digital contents representing the entity of a product are incorporated in a control program, and the control program is transmitted from a vendor to a buyer over a network. The product is delivered from the vendor to the buyer after a desired delivery period has elapsed from the transmission. After the product is delivered, the control program disables the digital contents. Therefore, when the present invention is applied to the book business, the buyer can read the digital contents representing the entity of the book immediately after the buyer places an order for the book. After that, the buyer can get the book that will be delivered.