Downward-directed transitive frames with universal relations
نویسنده
چکیده
In this paper we identify modal logics of some bimodal Kripke frames corresponding to geometrical structures. Each of these frames is a set of ‘geometrical’ objects with some natural accessibility relation plus the universal relation. For these logics we present finite axiom systems and prove completeness. We also show that all these logics have the finite model property and are PSPACE-complete. To prove this, we show that under certain restrictions, adding the universal modality preserves ‘good’ properties of a monomodal logic.
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