FBN, like most business applications, contains the typical subsystems: - product - order - customer - payment.
The Order subsystem depends on the customer subsystem: an order refers to it's customer.
Currently my Customer subsystem is also depending on the Order subsystem: a Customer has a list of orders.
Result: there is a bidirectional relationship between the Customer and Order subsystem.
Ideally, this would be a unidirectional relationship. However, both relations seem reasonable to me: - an order not referring to a customer at all seems a bit odd and - having a customer subsystem that does not allow for getting a customer's orders seems too limiting.