Hi Safa - What have you tried?
Here is the original image : https://github.com/ddossot/NxBRE/blob/master/Misc/architecture-overall.png The overlap with the Flow Engine is probably to show that one can use it as a binder for the Inference Engine, I guess? I can't remember, this was so long ago :P
Here it is: https://github.com/ddossot/NxBRE/blob/master/NxBRE3/Source/Util/PseudoCodeRenderer.cs It's used for rendering rules into a human friendly pseudo-code, for documentation purposes, to let, say, business experts, verify the rules are correct.
I've looked for all mentions of "binder" in the chapter and can't find a place where it says it's used with the flow engine. So either I can't search (and it's possible!) or you may have misread. Please point to the specific sentence that says so.
Ah sorry, I misunderstood, I thought you wanted to know exactly which set/rule had...
Even if the logic block had an ID, this wouldn't be what you want because you want...
https://github.com/ddossot/NxBRE/blob/master/NxBRE3/Test/FlowEngine/TestBackward...
Unfortunately there's no way to know the set ID from within the set. So you would...