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We give a model of dependent type theory with one univalent universe and propositional truncation interpreting a type as a stack, generalising the groupoid model of type theory. As an application, we show that countable choice cannot be…

Logic in Computer Science · Computer Science 2017-04-21 Thierry Coquand , Bassel Mannaa , Fabian Ruch

A type theory is presented that combines (intuitionistic) linear types with type dependency, thus properly generalising both intuitionistic dependent type theory and full linear logic. A syntax and complete categorical semantics are…

Logic in Computer Science · Computer Science 2026-05-07 Matthijs Vákár

Awodey, later with Newstead, showed how polynomial functors with extra structure (termed ``natural models'') hold within them the categorical semantics for dependent type theory. Their work presented these ideas clearly but ultimately led…

Logic in Computer Science · Computer Science 2026-03-03 C. B. Aberlé , David I. Spivak

This is an introductory textbook to univalent mathematics and homotopy type theory, a mathematical foundation that takes advantage of the structural nature of mathematical definitions and constructions. It is common in mathematical practice…

Logic · Mathematics 2022-12-22 Egbert Rijke

Higher inductive types (HITs) in Homotopy Type Theory (HoTT) allow the definition of datatypes which have constructors for equalities over the defined type. HITs generalise quotient types and allow to define types which are not sets in the…

Logic in Computer Science · Computer Science 2018-05-09 Thorsten Altenkirch , Paolo Capriotti , Gabe Dijkstra , Nicolai Kraus , Fredrik Nordvall Forsberg

When working in Homotopy Type Theory and Univalent Foundations, the traditional role of the category of sets, Set, is replaced by the category hSet of homotopy sets (h-sets); types with h-propositional identity types. Many of the properties…

Logic in Computer Science · Computer Science 2025-02-19 Daniel Gratzer , Håkon Gylterud , Anders Mörtberg , Elisabeth Stenholm

Univalent homotopy type theory (HoTT) may be seen as a language for the category of $\infty$-groupoids. It is being developed as a new foundation for mathematics and as an internal language for (elementary) higher toposes. We develop the…

Category Theory · Mathematics 2023-06-22 Egbert Rijke , Michael Shulman , Bas Spitters

By extending type theory with a universe of definitionally associative and unital polynomial monads, we show how to arrive at a definition of opetopic type which is able to encode a number of fully coherent algebraic structures. In…

Logic in Computer Science · Computer Science 2021-05-04 Antoine Allioux , Eric Finster , Matthieu Sozeau

We develop semantics and syntax for bicategorical type theory. Bicategorical type theory features contexts, types, terms, and directed reductions between terms. This type theory is naturally interpreted in a class of structured…

Logic in Computer Science · Computer Science 2023-10-13 Benedikt Ahrens , Paige Randall North , Niels van der Weide

Polynomial functors are useful in the theory of data types, where they are often called containers. They are also useful in algebra, combinatorics, topology, and higher category theory, and in this broader perspective the polynomial aspect…

Logic in Computer Science · Computer Science 2014-07-15 Joachim Kock

A $\mathcal{C}$-set is a functor from the category $\mathcal{C}$ to the category of finite sets and functions. The category of $\mathcal{C}$-sets, $\mathcal{C} - \operatorname*{set}$, is defined as the category whose objects are…

The intended model of the homotopy type theories used in Univalent Foundations is the infinity-category of homotopy types, also known as infinity-groupoids. The problem of higher structures is that of constructing the homotopy types needed…

Logic · Mathematics 2018-07-09 Ulrik Buchholtz

A hierarchy of type universes is a rudimentary ingredient in the type theories of many proof assistants to prevent the logical inconsistency resulting from combining dependent functions and the type-in-type rule. In this work, we argue that…

Programming Languages · Computer Science 2024-04-09 Jonathan Chan , Stephanie Weirich

We give an algebraic characterization of the syntax and operational semantics of a class of simply-typed languages, such as the language PCF: we characterize simply-typed syntax with variable binding and equipped with reduction rules via a…

Logic · Mathematics 2023-06-22 Benedikt Ahrens

We give an algebraic characterization of the syntax and semantics of a class of simply-typed languages, such as the language PCF: we characterize simply-typed binding syntax equipped with reduction rules via a universal property, namely as…

Logic in Computer Science · Computer Science 2012-08-28 Benedikt Ahrens

We give a natural-deduction-style type theory for symmetric monoidal categories whose judgmental structure directly represents morphisms with tensor products in their codomain as well as their domain. The syntax is inspired by Sweedler…

Category Theory · Mathematics 2021-07-13 Michael Shulman

We introduce the notion of groupoidal (weak) test category, which is a small category A such that the groupoid-valued presheaves over A models homotopy types in a "canonical and nice" way. The definition does not require a priori that A is…

Algebraic Topology · Mathematics 2025-11-05 Léonard Guetta

Higher inductive types are a class of type-forming rules, introduced to provide basic (and not-so-basic) homotopy-theoretic constructions in a type-theoretic style. They have proven very fruitful for the "synthetic" development of homotopy…

Logic · Mathematics 2020-07-08 Peter LeFanu Lumsdaine , Mike Shulman

We introduce a new model construction for Martin-L\"{o}f intensional type theory, which is sound and complete for the 1-truncated version of the theory. The model formally combines the syntactic model with a notion of realizability; it also…

Logic · Mathematics 2012-05-25 Pieter Hofstra , Michael A. Warren

This paper improves the treatment of equality in guarded dependent type theory (GDTT), by combining it with cubical type theory (CTT). GDTT is an extensional type theory with guarded recursive types, which are useful for building models of…

Logic in Computer Science · Computer Science 2017-10-09 Lars Birkedal , Aleš Bizjak , Ranald Clouston , Hans Bugge Grathwohl , Bas Spitters , Andrea Vezzosi