A Judgmental Construction of Directed Type Theory

Abstract

We reformulate recent advances in directed type theory--a type theory where the types have the structure of synthetic (higher) categories--as a logical calculus with multiple context 'zones', following the example of Pfenning and Davies. This allows us to have two kinds of variables--'neutral' and 'polar'--with different functoriality requirements. We focus on the lowest-dimension version of this theory (where types are synthetic preorders) and apply the logical language to articulate concepts from the theory of rewriting. We also take the occasion to develop the categorical semantics of dual-context systems, proposing a notion of dual CwF to serve as a common structural base for the model theories of such logics.