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
Two-barrier rule would be the production wing valve and the upper master valve. Uncontrolled release of pressure has been the cause of many accidents in the oilfield and so the two barrier rule is considered very important for increasing safety. Two-barrier rule The two barrier rule is a policy of safety for work on piping carrying high pressure and/or high temperature fluids. It is commonly used by oil companies. The rule simply states that for any work that must be done on a section of piping, which involves breaking containment, there must be at least two barriers separating the fluids from the