Formal aspects of the interpretation of Fourier maps

General set and graph theory have been applied to formalize the process of recognition of a set of electron density maxima in Fourier maps as a chemical (sub)structure in order to avoid human intervention. The information content of F and E maps is discussed in relation to the formulation of hypotheses on the labelling function relating the valued chemical structure graph to the non-valued Fourier graph. Various combinatorial methods based on graph theory, which find application in chemical structure information retrieval techniques, are indicated to establish relations between (sub)structures, leading to one-to-one mapping of the Fourier maxima to specific entities of the known organochemical structure.