  In this work we establish and investigate the connections between causality
for query answers in databases, database repairs wrt. denial constraints, and
consistency-based diagnosis. The first two are relatively new problems in
databases, and the third one is an established subject in knowledge
representation. We show how to obtain database repairs from causes and the
other way around. The vast body of research on database repairs can be applied
to the newer problem of determining actual causes for query answers. By
formulating a causality problem as a diagnosis problem, we manage to
characterize causes in terms of a system's diagnoses.
