  For a computational system to be intelligent, it should be able to perform,
at least, basic deductions. Nonetheless, since deductions are, in some sense,
equivalent to tautologies, it seems that they do not provide new information.
The present article proposes a measure the degree of semantic informativity of
valid deductions in a dynamic setting. Concepts of coherency and relevancy,
displayed in terms of insertions and deletions on databases, are used to define
semantic informativity. In this way, the article shows that a solution to the
problem about the informativity of deductions provides a heuristic principle to
improve the deductive power of computational systems.
