كليدواژه :
Chains , Kripke models , intuitionistic , Submodel
چكيده فارسي :
There are several ways to define the notion of submodel for
Kripke models of intuitionistic first-order logic. In our approach a Kripke
model A is a submodel of a Kripke model B if the frame of A is a subframe of
the frame of B and for each two corresponding worlds A® and B® of them,
A® is a classical submodel of B®. In this case, B is called an extension of
A. We characterize formulas that are preserved under taking extensions of
Kripke models. We also define a notion of union of chain for Kripke models
and introduce a class of formulas that is preserved in unions of chains.
