MQTT is messaging protocol. Is there standardized messages for controlling devices? Also, there can be different protocols for talking to devices and for talki

MQTT is messaging protocol. Is there standardized messages for controlling devices? Also, there can be different protocols for talking to devices and for talking between computers, gateways, and services. Most home automation devices don't speak Internet protocols and need a gateway as bridge and implement more complicated controls. Devices need to worry about low power, bandwidth, and limited processing power. Might be good idea for security if devices aren't available on Internet routed protocols.