I agree with the comment from "Ingo1966".
Interface Matrix is traditionally part of "Functional Analysis" carried out prior to Design
FMEA. It Illustrates relationships between the subsystems, assemblies, subassemblies, and components within the object as well as the
interfaces with the neighboring systems and environments. (Interface Regarding PEMI - Physical, Energy, Mass and Information) Further it identifies the type of Interface required:
+2 if Interaction is necessary for the function
+1 if Interaction is essential but, not absolutely necessary for the function
0 If Interaction does not effect functionality
-1 If Interaction causes negative effect but does not effect functionality
-2 If Interaction must be prevented to achieve functionality.
Attached is the sample Interface matrix for the Pen.
