I mean equal w.r.t. a chosen notion of equality. So for any pair (==s, ==t) of notions of equality, there is a different notion of full abstraction. Here ==s re

I mean equal w.r.t. a chosen notion of equality. So for any pair (==s, ==t) of notions of equality, there is a different notion of full abstraction. Here ==s relates programs of the source language and ==t relate programs of the target language.