The framework of art is also its most secret and its deepest poetry. 
                                                                                                        - Jacques Villon 

The framework of a painting or carving, like that of the human body or that of a building, is discreet; sometimes, indeed, it makes one forget its existence; but it cannot be absent, for it is what gives a work of art those "principal lines" of which Delacroix speaks. 

A painting is not simply a plane surface; it undertakes the conquest of space, and the different stages of its conquest are bound, in their turn, to be expressed in the composition: there is the conquest by means of geometry in three dimensions, and also the conquest by means of light and shade.

A painting acquires its unity even before it is a picture -- as soon as it is separated from its surroundings by a frame. In a frieze that unrolls across a wall like a ribbon, the parallel horizontal limits exert pressure on the contents, though letting them escape to right and left. Thus the frieze engenders a movement which takes place in duration as well as in extension, and this notion of duration, a new one for the for the plastic arts, brings us closer to the arts of time, to music and poetry. The frieze in fact is a rhythm rather than a composition.

                                                                                                        - Charles Bouleau
                                                                                                          "The Painters Secret Geometry"