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.
Object of the mind logic, whereas classical logic studies the extensional language of necessary and sufficient conditions. In general, a logical antecedent is a sufficient condition, and a logical consequent is a necessary condition(or the contingency) in a logical conditional. But logical conditionals accounting only for necessity and sufficiency do not always reflect every day if-then reasoning, and for this reason they are sometimes known as material conditionals. In contrast, indicative conditionals, sometimes known as non-material conditionals, attempt to describe if-then reasoning involving hypotheticals, fictions, or counterfactuals. Truth tables for if-then statements identify four unique combinations of premises and conclusions: true premises and true