Interfaces with external systems should be consistently handled throughout the system. The architecture need not
include a specific, detailed design for each system interface. It is often enough to simply identify the existence of
the interface as a significant part of the architecture and create a Component to encapsulate the detail, so that it can be developed later.
The Entity-Control-Boundary Pattern provides the basis for a useful technique to
support this. Specifically, if the system communicates with another system, define one or more components to
describe the communication protocol. The use of a component allows the interface to the external system to be
defined and stabilized, while leaving the design details of the system interface hidden as the system evolves.