Selected interfaces are managed.
Many integration and transition problems arise from unknown or uncontrolled aspects of both internal and external interfaces. Effective management of interface requirements, specifications,
and designs helps to ensure implemented interfaces are complete and compatible.
The supplier is responsible for managing the interfaces of the product or service it is developing. However, the acquirer identifies those interfaces, particularly external interfaces, that
it will manage as well.
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CMMI-ACQ 1.2
4. 
SG 2 Perform Interface Management