Directionality doesn't really matter if you can see both notes at once (e.g. side by side in Obsidian panes; an array of paper cards on your table).
Though, if time is your fundamental ordering pattern, you could use old-to-new flow whereby new stuff preferentially appends to old notes before they're codified as new/standalone/etc. notes. See also: TheSephist's incremental notes
I think the underlying point is one of common law-like precedence -- some (set of) note N, constrains the semantic/action/application/etc. space of (novel) (set of) note N'. Though, I'm not a mathematician...