Logic programming that computational steps cannot be logically deduced. However, in concurrent logic programming, any result of a terminating computation is a logical consequence of the program, and any partial result of a partial computation is a logical consequence of the program and the residual goal (process network). Consequently, the indeterminacy of computations implies that not all logical consequences of the program can be deduced. Concurrent constraint logic programming combines concurrent logic programming and constraint logic programming, using constraints to control concurrency. A clause can contain a guard, which is a set of constraints that may block the applicability of the clause.
Logical equivalence if and only if formula_2'". In particular, the truth value of formula_7 can change from one model to another. The claim that two formulas are logically equivalent is a statement in the metalanguage, expressing a relationship between two statements formula_1 and formula_2. The statements are logically equivalent if, in every model, they have the same truth value. Logical equivalence In logic, statements formula_1 and formula_2 are logically equivalent if they have the same logical content. That is, if they have the same truth value in every model (Mendelson 1979:56). The logical equivalence of formula_1 and formula_2 is sometimes expressed as