Further reading

For category theory, see Mac Lane [ 1998 ] and Riehl [ 2017 ] ; for sketches and computational models, see Ehresmann [ 1968 ] , Barr and Wells [ 1999 ] , and Spivak [ 2012 ] . Enriched categories, enriched functors, and weighted universal constructions are developed systematically by Kelly [ 1982 ] . Local-to-global and tangent foundations are developed by Mac Lane and Moerdijk [ 1992 ] , Cockett and Cruttwell [ 2014b ] , and Lee [ 2012 ] . For the two-dimensional graphical calculus used in this chapter, see Marsden [ 2014 ] and the systematic book-length account of Hinze and Marsden [ 2023 ] ; its tangent-category specialization is exemplified by Cockett and Cruttwell [ 2015 ] . For a more extended discussion of categorical learning, see Fong et al. [ 2019 ] , Cruttwell et al. [ 2022 ] , and Gavranović et al. [ 2024 ] .