This stream is a build-in access type that performs the most basic query to heartbeat_activity table possible. It simply fetches the messages in a limited way (for performance reasons) by time and max number. After fetching the messages, they go through a filter mechanism to remove restricted messages. At this point the real maximum of messages is set and merging starts. The final step is a the theme layer where we can alter almost everything.

As every stream, public heartbeat can be configured. To point out everything more specific, the configuration in this site is added on top. This way you can see what the effect is.

A heartbeat stream is a set of activity messages for a set of parameters. These parameters are bundled into a configuration or parameter object. A stream object is instantiated with the parameter object to perform a query to the activity logs table. Each of the streams are available as block and page. Streams are configured at location admin/build/heartbeat/streams.