Functional chain definition

I’m trying to create different functional chain to figure out what are all the given possibilities.
I created a Functional Chaind FC, which seems to quiet weird and sensless. FC is composed of 4 functions A,B,C and D. In this functional chain A<---->B are connected using a functional exchange. C and D have no link with any of those functions and do not have a path to access to it from A and B, neither in the other direction.
I do not understand the meaning behind this kind of functional chain. In my opinion, a functional chain draw the possible path among a bunch of functions for a data flow, and to executre an behavior.
I wonder if I’m clear enough. Don’t hesitate for additional questions.
Best kinds,

right clicking on this functional chain, you can create a Functional Chain Description to check if it is valid or not: it shall be a continuous oriented functional path. Otherwise, you functional chain will appear invalid on the diagram, and it will also raise an error after model validation.
Best regards,

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