Whenever
has connexity, a class can have at most one maximum, one minimum, one sequent, etc. Thus, in the cases we are concerned with in practice, we can speak of "the limit" (if any).
When
is a serial relation, we can greatly simplify the above definition of a limit. We can, in that case, define first the "boundary" of a class
, i.e. its limits or maximum, and then proceed to distinguish the case where the boundary is the limit from the case where it is a maximum. For this purpose it is best to use the notion of "segment."
We will speak of the "segment of