  We present a new method for computing core universal solutions in data
exchange settings specified by source-to-target dependencies, by means of SQL
queries. Unlike previously known algorithms, which are recursive in nature, our
method can be implemented directly on top of any DBMS. Our method is based on
the new notion of a laconic schema mapping. A laconic schema mapping is a
schema mapping for which the canonical universal solution is the core universal
solution. We give a procedure by which every schema mapping specified by FO s-t
tgds can be turned into a laconic schema mapping specified by FO s-t tgds that
may refer to a linear order on the domain of the source instance. We show that
our results are optimal, in the sense that the linear order is necessary and
the method cannot be extended to schema mapping involving target constraints.
