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According to Frege’s principle the denotation of a sentence coincides with its truthvalue. The principle is investigated within the context of abstract algebraic logic, and it is shown that taken together with the deduction theorem it characterizes intuitionistic logic in a certain strong sense. A 2nd-order matrix is an algebra together with an algebraic(More)
We present a model-theoretic study of correct behavioral subtyping for first-order, deterministic, abstract data types with immutable objects. For such types, we give a new algebraic criterion for proving correct behavioral subtyping that is both necessary and sufficient. This proof technique handles incomplete specifications by allowing proofs of correct(More)
A deductive system S (in the sense of Tarski) is Fregean if the relation of interderivability, relative to any given theory T , i.e., the binary relation between formulas { 〈α, β〉 : T, α `S β and T, β `S α }, is a congruence relation on the formula algebra. The multiterm deduction-detachment theorem is a natural generalization of the deduction theorem of(More)
The recent development of abstract algebraic logic has led to a reconsideration of the universal algebraic theory of ordered algebras from a new perspective. The familiar equational logic of Birkhoff can be naturally viewed as one of the deductive systems that constitute the main object of study in abstract algebraic logic; technically it is a deductive(More)