Event Policy Control

The aim of this pattern is to check and enforce policies on events. A message or event is received and based on that event and the state of data held by the policy manage, certain action is taken. It is possible to update the policy as well as the data on which a decision is made.

This pattern could be used when it is desirable to apply a specific policy on the fly based on an event and based on the sate of some piece of data.

Policy Engine: perform action based on event (from event producer) and condition (from the policy) and data (from data producer).
Event Producers: produce an event that must be acted upon.
Policy Producers: produce policies.
Event Consumers: register for "processed events", event consumers can also be policy producers.
Data Producers: update the data on which decisions are made.

Consumers register for "filtered" events.
Event Producers produce events
Policy Engine takes in events and fires off further events based on policies and data.