Predicate Logic - Stanford University

CHAPTER14FF FFPredicateLogicWe now turn our attention to a generalization of propositional Logic , called predi-cate, or first-order, Logic . predicates are functions ofzero or more variables thatreturn Boolean values. Thus predicates can be true sometimes and false sometimes,depending on the values of their arguments. For example, we shall find in predicatelogic atomic operands such ascsg(C, S, G). Here,csgis the Predicate name, andC,S, andGare arguments. We can think of this expression as a representationin Logic of the database relation Course-Student-Grade of Fig. It returns thevalueTRUE whenever the values ofC,S, andGare such that studentSgot gradeGin courseC, and it predicates as atomic operands, instead of propositional variables, givesus a more powerful language than expressions involving onlypropositions.

Some tautologies of predicate logic are analogs of tautologies for propo-sitional logic (Section 14.6), while others are not (Section 14.7). Proofs in predicate logic can be carried out in a manner similar to proofs in propositional logic (Sections 14.8 and 14.9). In Section 14.10 we discuss some of the implications of predicate logic as to our

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