Joyal-Tierney calculus in nLab
Idea. In the context of factorization systems such as they appear notably in enriched model category one frequently needs to handle iterated lifting problems.In the appendix of (Joyal–Tierney, 06) a symbolic calculus is introduced to facilitate these computations.A central point of it is to have the statement of prop. below be easily expressible in terms of "division on …