Software Engineering

8.2.4 
Identify external interfaces
The interfaces to external systems must be identified and the requirements associ-
ated with each interface need to be specified. External systems are those systems 
not being developed as part of the program, but they need to exchange data with 
the software product being developed. Interface specifications should address not 
only the physical means of data transfer, but also specify the message formats, data 
types, units of measures, and precision associated with each data type.
The operational model should be analyzed to specify each of the human–
machine interactions for operational, support, and diagnostic actions. In addition, 
the human–machine interface requirements should address how the application 
must detect and deal with improper or incorrect manual data inputs. The means 
of the manual interactions and the interfacing devices, such as keyboard, mouse, 
touch screen, and card reader, should be identified. The human–machine interface 
requirements should also address data displayed to the user and the types of output 
reports that must be generated by the software product.