Are we at risk of "changing subject" here?
An idea, itself is a Subject; it is an event *ideated* somewhere. Then, the idea has *aboutness*, which could be either a single subject (parent node is about the concept (subject) labeled "idea".
The parent node asserts a triple {idea, can have, multiple representations}
But, that parent node is a triple, an assertion. It is asserting that some subject, labeled "idea" exists in a relationship with multiple representations [of it] -- being the same subject.
So, what, really, is the meaning of the assertion unless there is an entailed change of subject with each different representation?