Relevance can be learned, specified, you could make them up, or use
some combination of the prior. True relevancy is ultimately decided by
the consumer/user/evaluator, however this can be extremely difficult
to establish. Unlike information retrieval which returns imperfect
results, data retrieval should always return perfect results.
Additional environmental information such as previous queries used,
previous results, information about the user, etc, can all be used to
better improve relevancy. -Thomas Hayden
