Formation rule

In

A formal language is an organized

Formal systems

A formal system (also called a logical calculus, or a logical system) consists of a formal language together with a

The formation rules of a propositional calculus may, for instance, take a form such that;

• if we take Φ to be a propositional formula we can also take ${\displaystyle \neg }$Φ to be a formula;
• if we take Φ and Ψ to be a propositional formulas we can also take (Φ ${\displaystyle \wedge }$ Ψ), (Φ ${\displaystyle \to }$ Ψ), (Φ ${\displaystyle \lor }$ Ψ) and (Φ ${\displaystyle \leftrightarrow }$ Ψ) to also be formulas.

A

then we can take (${\displaystyle \forall }$α)Φ and (${\displaystyle \exists }$α)Φ each to be formulas of our predicate calculus.

See also

• Finite state automaton

References