  Knowledge base exchange is an important problem in the area of data exchange
and knowledge representation, where one is interested in exchanging information
between a source and a target knowledge base connected through a mapping. In
this paper, we study this fundamental problem for knowledge bases and mappings
expressed in OWL 2 QL, the profile of OWL 2 based on the description logic
DL-Lite_R. More specifically, we consider the problem of computing universal
solutions, identified as one of the most desirable translations to be
materialized, and the problem of computing UCQ-representations, which optimally
capture in a target TBox the information that can be extracted from a source
TBox and a mapping by means of unions of conjunctive queries. For the former we
provide a novel automata-theoretic technique, and complexity results that range
from NP to EXPTIME, while for the latter we show NLOGSPACE-completeness.
