in this paper. Following the Knight's approach. we solve a convergence prob
lem Tot set-indexed martingales. For this purpose, we first define a tightn
ess criterion For set-indexed continuous processes. The core oi this: chara
cterization is connected with a weaker definition of continuity and hence t
he use of the corresponding topology, and with the Fact that indices take v
alues in a semilattice of closed subsets. Then. we give an effective lightn
ess criterion by means of an estimate For a majorizing measure defined on t
he space. We finally prove under this set-indexed framework a theorem simil
ar to the Knight's.