I just wonder, what is the difference between "facts" and "predicates" section in prolog ?
and what is the difference between "single" and "determ" keyword ?
Just to point the obvious: "Facts section" is for facts, facts are predicates that are always true, are used to describe some properties.
Single and determ are "fact mode", used optionally in a fact declaration, Single means the fact always has one and only one value, determ means the fact can have zero or one value.