If you have two Bounded Contexts where one depends on the other but not the other way around, then you usually have a customer-supplier relationship between the two. There will be consensus on the agreed upon interface via which the customer can access the supplier, and the supplier agrees to serve that interface and respect it. Changes to it must be discussed with the customer.

A natural extension to this is an Open Host Service. If the supplier has many customers, it will be too cumbersome to discuss and implement interfaces whith each customer individually. Instead, the supplier decides to define one interface all those customers can access. The difference to Conformist is that a Open Host Service does care about its customers and defines and respects the services it puts in place. With conformist, the leading context is free to change things in any way it desires.

This is open for grabs. There is not one defined protocoll for suppliers and customers to communicate. Depending on the circumstances, you may integrate via

• published database views of the supplier¹⁾,²⁾
• published services by the supplier ³⁾ the customer can use⁴⁾
• published events of the supplier the customer may consume⁵⁾