Yes, the purity has to be front and center though. I think it's worth being explicit that they must be deterministic (on their inputs) and that the scheduling algorithm itself needs to be both constrained and expressive enough to generate a schedule without doing any work. I only harp on this because it's not entirely obvious to folks who haven't been chugging on the design of the engine since the beginning, and I think it's a critical mistake to allow late-fingerprinting in the initial pass of the engine