Subscribing to and Querying Topics

This section describes commands used to retrieve content messages from AMPS, including both queries and subscriptions.

For details on the differences between these commands, see the AMPS User Guide.

Command	Usage
subscribe	Receive a stream of messages from a topic.
sow	Query a snapshot of the values within a topic in the State of the World (SOW).
sow_and_subscribe	Query a snapshot of the values within a topic in the SOW and begin a subscription atomically at the point of query.
delta_subscribe	Receive a stream of messages from a topic. If the topic is in the SOW, and it is possible to construct a partial message, receive only fields that have changed (fields that identify the message are also included by default).
sow_and_delta_subscribe	Query a snapshot of the values within a topic in the SOW and begin a subscription atomically at the point of query. If the topic is in the SOW, and it is possible to construct a partial message, receive only fields that have changed (fields that identify the message are also included by default).