A pair of constraint qualifications in convex semi-infinite programming, na
mely the locally Farkas-Minkowski constraint qualification and generalized
Slater constraint qualification, are studied in the paper. We analyze the r
elationship between them, as well as the behavior of the so-called active a
nd sup-active mappings, accounting for the tightness of the constraint syst
em at each point of the variables space. The generalized Slater constraint
qualification guarantees a regular behavior of the supremum function (defin
ed as supremum of the infinitely many functions involved in the constraint
system), giving rise to the well-known Valadier formula.