Structural rule A famous structural rule is known as cut. Considerable effort is spent by proof theorists in showing that cut rules are superfluous in various logics. More precisely, what is shown is that cut is only (in a sense) a tool for abbreviating proofs, and does not add to the theorems that can be proved. The successful 'removal' of cut rules, known as "cut elimination", is directly related to the philosophy of "computation as normalization" (see Curry–Howard correspondence); it often gives a good indication of the complexity of deciding a given logic. Structural rule In proof theory, a structural rule is
Looney 11 rule to a factor close to the square root of two, thus the above rule. The intensity of visible sunlight striking the surface of the Moon is essentially the same as at the surface of the Earth. The albedo of the Moon's surface material is lower (darker) than that of the earth's surface, and the Looney 11 rule increases exposure by one stop versus the Sunny 16 rule. Many photographers simply use the f/16-based Sunny 16 rule, unmodified, for lunar photographs. Looney 11 rule In lunar photography, the Looney 11 rule (also known as the Looney f/11 rule) is a method