For the symbol system also to be notational, more than syntactic disjointness and finite differentiation is required. Symbol systems are notational when 1) the characters are correlated to the field of reference unambiguously (with no character being correlated to more than one class of reference, or “compliance class”), 2) what a character refers to—the compliance class—must not intersect the compliance class of another character (i.e., the characters must be semantically disjoint), and 3) it i