Cross-Chain Message Passing (XCMP) scheme is a subset of the Polkadot protocol. It defines how messages can be passed among parachains with no additional trust assumptions beyond the economic security of the relay chain.
The XCMP scheme achieves the following properties:
Trustlessness Since the same set of validators secure one parachain as another while they also guarantee correct message passing, XCMP requires no more trust than a single blockchain would.
Consistency We provide absolute guarantee that the messages received were exactly those sent, even despite any chain reorgs.
Availability Polkadot guarantees that the messages will not be lost and are kept available. This is achieved by distributing erasure-coded pieces that can be used to reconstruct messages.
Maintaining the right ordering for messages output by parachain blocks is guaranteed by Input/Output validation.
Efficiency The protocol avoids too much bandwidth overhead and allows messages to arrive as quickly as possible.
Here is a little bit more information:
https://research.web3.foundation/en/latest/polkadot/networking/4-xcmp.html#
https://medium.com/web3foundation/polkadots-messaging-scheme-b1ec560908b7
This would allow FME to talk with blockchain technology create parachains that could tie into spatial data.
