The aim of this paper is to refine and extend proposals by Sozeau and Tabareau and by Voevodsky for universe polymorphism in type theory. In those systems judgments can depend on explicit constraints between universe levels. We here present a system where we also have products indexed by universe levels and by constraints. Our theory has judgments for internal universe levels, built up from level variables by a successor operation and a binary supremum operation, and also judgments for equality of universe levels.
@InProceedings{bezem_et_al:LIPIcs.TYPES.2022.13, author = {Bezem, Marc and Coquand, Thierry and Dybjer, Peter and Escard\'{o}, Mart{\'\i}n}, title = {{Type Theory with Explicit Universe Polymorphism}}, booktitle = {28th International Conference on Types for Proofs and Programs (TYPES 2022)}, pages = {13:1--13:16}, series = {Leibniz International Proceedings in Informatics (LIPIcs)}, ISBN = {978-3-95977-285-3}, ISSN = {1868-8969}, year = {2023}, volume = {269}, editor = {Kesner, Delia and P\'{e}drot, Pierre-Marie}, publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik}, address = {Dagstuhl, Germany}, URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.TYPES.2022.13}, URN = {urn:nbn:de:0030-drops-184564}, doi = {10.4230/LIPIcs.TYPES.2022.13}, annote = {Keywords: type theory, universes in type theory, universe polymorphism, level-indexed products, constraint-indexed products} }
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