Hello, thank you for the question. In fact, NVO will allow assets trading, for now, you are seeing it from a centralized point of view.
The model of NVO is A sends to B, so if you have a Waves Asset, and wants to sell it for BTC, and found someone who wants your Assets and offers BTC, both will exchange asset for crypto.
It is as simple as that. The ratio is decided by the traders.
Very nice!
I'm now wandering how can you cope with race conditions and double spend attempts in cross chain trades.
Suppose I sell my asset X through NVO, buyer sends me asset Y and in the meantime I transfer my asset X somewhere else through a native wallet.
There's a chance I get asset Y for free.