We describe new applications of the theory of automata to natural
language processing: the representation of very large scale dictionaries
and the indexation of natural language texts. They are based on new algorithms
that we introduce and describe in detail. In particular, we give pseudocodes
for the determinisation of string to string transducers, the deterministic
union of p-subsequential string to string transducers, and the
indexation by automata. We report on several experiments illustrating the
applications.