If the clause is an ʻinformationʼ clause (a proposition, congruently realized as indicative), this means either (i) ʻeither yes or noʼ, i.e. ʻmaybeʼ; or (ii) ʻboth yes and noʼ, i.e. ʻsometimesʼ; in other words, either probability or usuality [...] We refer to type (1) [the information clause] as MODALIZATION [...]. - Halliday (1985), a pag.335