Fig. 3.17 The 'Made' relationship is redundant.
Similarly, it is possible to find the sender of a payment using the composition of the two relationship types 'was_posted_to' and 'was_sent_to', navigating from PAYMENT to INVOICE to CUSTOMER.
If an extra (direct) relationship type from CUSTOMER to PAYMENT were to be implemented it would be redundant. If it showed only which customer sent a payment and (via its inverse) which payments a customer made, it would be unnecessary because it shows nothing that cannot be shown using compositions of the other two relationship types.