Properties

• mmrc / device ID / node ID / property ID: this is the base topic of a property. Each property must have a unique property ID on a per-node basis which adhere to the ID format.

• A property payload (e.g. a sensor reading) is directly published to the property topic, e.g.:

  mmrc/super-car/engine/temperature → "21.5"

Property Attributes

• mmrc / device ID / node ID / property ID / $property-attribute:

The following attributes are required:

Topic	Description	Payload type
$name	Friendly name of the property.	String
$datatype	The data type. See Payloads.	Enum: [integer, float, boolean,string, enum, color]

The following attributes are optional:

Topic	Description	Payload type
$format	Specifies restrictions or options for the given data type	See below
$settable	Settable (true). Default is read-only (false)	Boolean
$retained	Non-retained (false). Default is Retained (true).	Boolean

For example, our temperature property would send:

mmrc/super-car/engine/temperature/$name → "Engine temperature"

mmrc/super-car/engine/temperature/$settable → "false"

mmrc/super-car/engine/temperature/$unit → "°C"

mmrc/super-car/engine/temperature/$datatype → "float"

mmrc/super-car/engine/temperature/$format → "-20:120"

mmrc/super-car/engine/temperature → "21.5"

Settable and retained:

• Properties can be settable. For example, you don't want your temperature property to be settable in case of a temperature sensor (like the car example), but to be settable in case of a thermostat.

• Properties can be retained. A property is retained by default. A non-retained property would be useful for momentary events (door bell pressed).

A combination of those flags compiles into this list:

• retained + non-settable: The node publishes a property state (temperature sensor)
• retained + settable: The node publishes a property state, and can receive commands for the property (by controller or other party) (lamp power)
• non-retained + non-settable: The node publishes momentary events (door bell pressed)
• non-retained + settable: The node publishes momentary events, and can receive commands for the property (by controller or other party) (brew coffee)

Format:

• For integer and float: Describes a range of payloads e.g. 10:15
• For enum: payload,payload,payload for enumerating all valid payloads.
• For color:
  • rgb to provide colors in RGB format e.g. 255,255,0 for yellow.
  • hsv to provide colors in HSV format e.g. 60,100,100 for yellow.

Property command topic

• mmrc / device ID / node ID / property ID / set: The device must subscribe to this topic if the property is settable (in case of actuators for example).

A MMRC controller publishes to the set command topic with non-retained messages only.

The assigned and processed payload must be reflected by the MMRC device in the property topic mmrc / device ID / node ID / property ID as soon as possible. This property state update not only informs other devices about the change but closes the control loop for the commanding controller, important for deterministic interaction with the client device.

To give an example: A kitchen-light device exposing the light node with a settable power property subscribes to the topic mmrc/kitchen-light/light/power/set for commands:

mmrc/kitchen-light/light/power/set ← "true"

In response the device will turn on the light and upon success update its power property state accordingly:

mmrc/kitchen-light/light/power → "true"