Some strange quantifiers

Abstract

We report a recent Tarski-style semantics for a language which includes the branching quantifiers on which Andrzej Ehrenfeucht made the first breakthrough in 1958. The semantics is equivalent to Henkin's game-theoretic semantics, but unlike Henkin's it is compositional. We use second-order formulas to give a new (and with any luck, more manageable) description of this Tarski-style semantics. Finally we apply the new description to present a compositional and fully abstract semantics for the slightly more limited syntax of Hintikka and Sandu, answering a question of Sandu.