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In mathematical logic, a propositional variable (also called a sentence letter, [1] sentential variable, or sentential letter) is an input variable (that can either be true or false) of a truth function. Propositional variables are the basic building-blocks of propositional formulas, used in propositional logic and higher-order logics.
The predicate calculus goes a step further than the propositional calculus to an "analysis of the inner structure of propositions" [4] It breaks a simple sentence down into two parts (i) its subject (the object (singular or plural) of discourse) and (ii) a predicate (a verb or possibly verb-clause that asserts a quality or attribute of the object(s)).
Any variable is a term. Any constant symbol from the signature is a term; an expression of the form f(t 1,...,t n), where f is an n-ary function symbol, and t 1,...,t n are terms, is again a term. The next step is to define the atomic formulas. If t 1 and t 2 are terms then t 1 =t 2 is an atomic formula
connectives for propositional variables. Some many-valued logics may have incompatible definitions of equivalence and order (entailment). Both conjunction and disjunction are associative, commutative and idempotent in classical logic, most varieties of many-valued logic and intuitionistic logic.
Because of this, the propositional variables are called atomic formulas of a formal propositional language. [14] [2] While the atomic propositions are typically represented by letters of the alphabet, [d] [14] there is a variety of notations to represent the logical connectives. The following table shows the main notational variants for each of ...
Horn satisfiability is actually one of the "hardest" or "most expressive" problems which is known to be computable in polynomial time, in the sense that it is a P-complete problem. [2] The extension of the problem for quantified Horn formulae can be also solved in polynomial time. [3]
In computer science and mathematical logic, satisfiability modulo theories (SMT) is the problem of determining whether a mathematical formula is satisfiable.It generalizes the Boolean satisfiability problem (SAT) to more complex formulas involving real numbers, integers, and/or various data structures such as lists, arrays, bit vectors, and strings.
Classical propositional calculus is the standard propositional logic. Its intended semantics is bivalent and its main property is that it is strongly complete, otherwise said that whenever a formula semantically follows from a set of premises, it also follows from that set syntactically. Many different equivalent complete axiom systems have ...