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
Emery's rule rule. When the parasite is a close relative of the host but not its sister species, the relationship is in "loose" adherence to the rule. Emery's rule In 1909, the entomologist Carlo Emery noted that social parasites among insects (e.g., kleptoparasites) tend to be parasites of species or generation to which they are closely related. Over time, this pattern has been recognized in many additional cases, and generalized to what is now known as Emery's rule. The pattern is best known for various taxa of Hymenoptera. For example, the social wasp "Dolichovespula adulterina "parasitizes other members of its genus such