xsd:string LUs in this frame describe a non-commutative process (as opposed to a generic statement) of arithmetic, e.g. subtraction and division, involving two numbers, labeled Term_1 and Term_2. Because of the non-commutative nature of these processes, Term_1 and Term_2 are not separated on a grammatical basis but rather on a mathematical basis (see FE definitions). When referencing the process, the numbers can be vague and are often omitted through indefinite null instantiation.