We investigate on the possibility of transforming concepts in Description Logics into relational databases and queries in such a way that subsumption between the original concepts can be decided as query answering over a database. For the positive results, we show a translation of
${\cal ALN}$
-concepts into pairs (database, query) such that, in order to decide Subsumption
$C \sqsubseteq D$
one evaluates the query resulting from the translation of D over the database resulting from C. For the negative results, we show that no compilation is possible for expressive Description Logics.
