premise: In the first of these sentences if by is the complement of come and Tuesday is an <mask> of time equivalent to on Tuesday , there will be strong stress on by in the spoken language ; but if a complement for come is implied and by Tuesday is a prepositional unit used as an <mask> , by will be unstressed or lightly stressed at most .
hypothesis: the proper context for <mask> here should be something added to another thing but not an essential part of it