What does "notional categories" mean?
The context: Wilkins (a British linguist) divided the systems of meaning that lay behind the communicative uses of languages into to two categories (which were later expanded into a book Notional Syllabuses):
1. notational categories (concepts of time, sequence, quantity, location, frequency)
2. categories of communicative functions (requests, denials, offers, complaints)
My dictionary says "notational" means "based on guses, estimates, or theories instead of realities". My question is how to understand the word in this linguistic context (I don't quite understand why concepts of time sequence... would be categorized into "notational categories").
I appreciate your answer:-)