# description
The type of method used to execute a subscription.

# concept[].definition
The channel is executed by making a post to the URI. If a payload is included, the URL is interpreted as the service base, and an update (PUT) is made.

# concept[].definition
The channel is executed by sending a packet across a web socket connection maintained by the client. The URL identifies the websocket, and the client binds to this URL.

# concept[].definition
The channel is executed by sending an email to the email addressed in the URI (which must be a mailto:).

# concept[].definition
The channel is executed by sending an SMS message to the phone number identified in the URL (tel:).

# concept[].definition
The channel is executed by sending a message (e.g. a Bundle with a MessageHeader resource etc.) to the application identified in the URI.