Summary: Logical Step-Indexed Logical Relations
IT University of Copenhagen
We show how to reason about "step-indexed" logi-
cal relations in an abstract way, avoiding the tedious,
error-prone, and proof-obscuring step-index arithmetic that
seems superficially to be an essential element of the method.
Specifically, we define a logic LSLR, which is inspired by
Plotkin and Abadi's logic for parametricity, but also sup-
ports recursively defined relations by means of the modal
"later" operator from Appel et al.'s "very modal model"
paper. We encode in LSLR a logical relation for reasoning