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  • $\begingroup$ Does stand for the identity type or judgemental equality? What is δ? $\endgroup$ Commented Sep 2, 2023 at 17:37
  • $\begingroup$ You should explain what Γ (Δ ⊦ α : A) (Δ ⊦ β : a₀ ≡ α) ⊦ B type is supposed to mean. What is a context, precisely? What are the judgement forms? You're changing these notions in a fundamental way, so you should explain the changes. $\endgroup$ Commented Sep 2, 2023 at 17:39
  • $\begingroup$ stands for the identity type, like in Agda. Regarding δ: just like we use the notation x. t to stand for a family t in the background context extended by some x : ?, I have δ.t standing for a family t in the background context extended by a telescope δ : ?. In that particular case δ : Δ. A context is a snoc-list of families of types (where families can depend on preceding families). Families can be eliminated just like variables in normal MLTT, but now we need to provide an instance of the context the family depends on. $\endgroup$
    – Russoul
    Commented Sep 2, 2023 at 20:21
  • $\begingroup$ Of course there is a lot to it, but hopefully that conveys the idea. All that's new is that we replace dependence on type (x : A) with dependence on family (Δ ⊦ x : A) $\endgroup$
    – Russoul
    Commented Sep 2, 2023 at 20:22
  • $\begingroup$ I vaguely remember that Mike Shulman at some point was asking & thinking about having such multi-level contexts. Is he listening? $\endgroup$ Commented Sep 2, 2023 at 22:38