For some reason, before reading this, I misunderstood the “cascade” as a metaphor for composition, were the water fallen from a first cascade might flow as input to a second cascade; but now I see this is clearly wrong and the cascade means exactly the contrary, since the punctuation :: and ; breaks that continuity. It means a jump in the regular flow of evaluation, as a cascade means a jump.

The double colon syntax is specific to Cuis; at least it is not valid syntax in Squeak.