  We review some modern theories about the structure of space and time, in
particular those related to discrete space and time. Following an
epistemological method we start from theories which discuss discrete space and
time as a mathematical tool to solve physical models. Antother theories look
for physical content of the discrete structure of space and time, based in
relational theories of space and time which are derived from the relations of
some fundamental entities. Finally we present some philosophical positions who
try to find the ontological foundation of the relational theories os space and
time.
