Policy

[ryan-mars]

• [x] subscription filter for events #27
• [x] has an event handler lambda function

• [x] Handler can invoke commands #26

  Policy

Illustrations ©️ Avanscoperta

[sam-goodwin]

Is there a snippet from the event storming material we can include here, like we did for Bounded Context #7? I thought that was especially helpful.

[ryan-mars]

Policies are probably the most interesting thing to model in EventStorming. They cover all the spectrum of organisation reactions from human behaviours to automation including:

• habits
• unconscious reactions
• Tacit agreements
• Explicit agreements
• Codified or corporate rules
• Inconsistent rules (different actors implementing the same rule in different ways)
• Listeners (stateless listeners performing easy tasks, like sending notifications)
• Process Managers and Sagas

The link between an event and its consequences can be encapsulated by a policy, but when the event-reaction combination is too obvious, we might miss the link. Forcing ourself to obey the rule: There has to be a lilac between the orange and the blue ...is a good way to force yourself into asking deeper questions about the nature of the policy.