  Interestingness is an important criterion by which we judge knowledge
discovery. But, interestingness has escaped all attempts to capture its
intuitive meaning into a concise and comprehensive form. A unifying paradigm is
formulated by function composition. We claim that composition is bipolar, i.e.
composition of exactly two functions, whose two semantic poles are relevance
and unexpectedness. The paradigm generality is demonstrated by case studies of
new interestingness functions, examples of known functions that fit the
framework, and counter-examples for which the paradigm points out to the
lacking pole.
