Flowchart symbol or pattern for Publisher/Subscriber or Listen/Notify

Question

We have a system consisting of

• Detectors
• Converters/Transformers
• Business Rules Engines and State Managers
• Views/Displays/Applications

There are several potential ways these may interact and share state

• Message passing mediated by Queues
• Point to Point Message Passing via Http
• Shared State in a Database/Datastore and state-change notifications via messaging

I am drawing up a simplistic flow-chart / system diagram and am wondering how best to represent the publish-subscribe or notifier/listener(s) mechansisms. I do not recall standardized flowchart symbols for these.

An example would be:

1  A Parts Modification detection event occurs

2  Events are written to `Events` and `Parts_State` topics (or possibly tables)

3  A State_Management module that listens on those topics performs validations and 
   transformations then updates downstream topics with the results

What I am looking for is how to represent the Publisher/Notifier aspect of the Detection module in the Flowchart and the Subscriber/Listener aspect of the State_Management module in the flowchart.