In 1980, Chandra and Harel investigated, in the context of the relational database model, which queries are “reasonable”. They characterized this class of queries by means of the concept of genericity, which has since taken a central position in the theory of computable queries. A query in the relational model is called computable if and only if it is a Turing-computable function on some representation of the database that is also generic. By a generic function Q, we mean here a function whose result is invariant under any permutation π of the universal domain of the database. Informally, this means that the value of a generic query is independent of the internal representation of the data and only depends on the logical structure of the database. Formally, on the other hand, this means that if A and B are two relational databases such that B = π(A), for some isomorphism π, then Q(B) π(Q(A)).