Matter Interaction Model and interaction types

The Interaction Model layer defines what interactions can be performed between a client and a server device. The node that initiates the interaction is called initiator (typically, a client device), and the node that is the recipient of the interaction is called target (typically, a server device).

The following interaction types belong to the Interaction Model:

Read

This interaction is used get the value of attributes or events.

Write

This interaction is used to modify attribute values.

Invoke

This interaction is used to send commands.

Subscribe

This interaction is used to create subscription with a target in order to receive data reports from the target periodically instead of polling for data. Subscriptions can be related to attributes and events.

Each interaction is made of transactions, which in turn are made of actions. Each action can be conveyed by one (n) or more messages (n, n+1).

Interaction structure

Interaction examples: Door Lock

The following sections present examples of the interaction types described above. The examples use an imaginary Matter controller as the interaction initiator and a door lock device as the interaction target.

Read interaction

The read interaction can be used by the Matter controller to read one or more attributes or events from the Data Model layer of the door lock device. For example, the Matter controller can read the LockType attribute of the DoorLock cluster to display an adequate icon to the user. The following diagram presents actions that need to be exchanged in order to complete this interaction.

Write interaction

The write interaction can be used to modify one or more attributes of the door lock device. For example, the Matter controller can change the OperatingMode attribute of the DoorLock cluster to put the lock in the privacy mode in which the door can only be unlocked manually from inside the building. The following diagram presents actions that need to be exchanged in order to complete this interaction.

Invoke interaction

The invoke interaction allows the Matter controller to invoke one of the commands from the Data Model layer of the door lock device. For example, the Matter controller can use the UnlockDoor command of the DoorLock cluster to remotely unlock the door. The following diagram presents actions that need to be exchanged in order to complete this interaction.

Note

This is a special case of the invoke interaction, a Timed interaction, which requires two more messages to be exchanged before the actual command is sent. These two messages are needed to make sure that an attacker cannot intercept and replay the command later to unlock the door when the house owner is away.

Subscribe interaction

The subscribe interaction can be used to monitor the state of one or more attributes or events of the door lock device. For example, the Matter controller can subscribe to the LockState attribute of the DoorLock cluster to receive notifications whenever the door is unlocked by another user. The diagram below presents actions that need to be exchanged in order to complete this interaction.

Note

This is a long-running interaction that consists of multiple transactions executed until either side stops responding or responds with a failure status.