  Functorial semi-norms are semi-normed refinements of functors such as
singular (co)homology. We investigate how different types of representability
affect the (non-)triviality of finite functorial semi-norms on certain functors
or classes. In particular, we consider representable functors, generalised
cohomology theories, and so-called weakly flexible homology classes in singular
homology and l1-homology.
