Authors: Covaljiu O. I., Rata M. F.
Abstract
The 3-valued extension of provability-intuitionistic logic is studied. It reprezents the logic $L^{\Delta}$ of the $\Delta$-pseudo-boolean algebra
$$
Z_3^{\Delta} = < \{0, \tau, 1\}; \&, \lor, \supset, \neg,
\Delta > (0 < \tau < 1, \Delta 0 = \tau, \Delta \tau =
\Delta 1 = 1).
$$
We call a model of a boolean function $f(p_1, \dots, p_n)$ in the logic $L^{\Delta}$ every formula, which express
such $\Delta$-pseudo-boolean function $F(p_1, \dots, p_n)$, that for every set $<\alpha_1, \dots, \alpha_n>$ of 0s and
1s the equality $f(\alpha_1, \dots, \alpha_n) = F(\alpha_1, \dots, \alpha_n)$ is true. Let $K$ be a class of formulas, closed with respect to expressibility in logic $L^{\Delta}$. The system $\Sigma$ of formulas of the class $K$ is called model complete in $K$, if for every boolean function, which has a model in $K$, can be expressed via
$\Sigma$ at least one model of it in $L^{\Delta}$. The criteria of model completeness in two classes of formulas,
which model autodual boolean functions and boolean functions permutable with 1 in the logic $L^{\Delta}$ are istablished . The rezults are expressed in terms of three and thirteen classes of formulas.
Institutul de Matematică Academia de Ştiinţe a Moldovei
str. Academiei 5, Chişinău MD-2028, Moldova