by definition: an exchange doesn't need any reference to outside market data

even for systems built on a sequencer which do (e.g. an OMS), the volume is too large

the usual strategy is for processes which require it, is to sample it and them stamp it on commands

which maintains the invariants

(my background: I have been a developer on one of Mike Blum's original sequencers)

Fair point that you don't actually need the market data you send out if you have the original order book data internally.

How would an exchange enforce the trade through rule without any outside market data?