Encyclopedia
Canon
Canon (Gr. - norm, rule) - a set of firmly established rules defining the norms of composition and color scheme, system of proportions or iconography of a given type of image. In church architecture, the role of canon is performed by "canonical tradition" - exemplary structures accepted by the Church as reflecting through architecture the theological content of the church
Source: "SP 31-103-99. Buildings, Structures and Complexes of Orthodox Churches"
(adopted by the Decree of Rosstroy of Russia dated December 27, 1999 No. 92)