A different formalization of abduction is based on inverting the function that calculates the visible effects of the hypotheses. Formally, we are given a set of hypotheses formula_46 and a set of manifestations formula_47; they are related by the domain knowledge, represented by a function formula_48 that takes as an argument a set of hypotheses and gives as a result the corresponding set of manifestations. In other words, for every subset of the hypotheses formula_49, their effects are known to be formula_50.