Check our Francis Cheung's blog posts on loosely couple communication for composite WPF applications. Francis discusses three mechanisms for loosely coupled communication:
Francis (did most of the work) and I identified some guidelines on when to use each of these mechanisms. Let us know your thoughts on the guidance as this is input to our Prism documentation.
Guidelines for loosely coupled communication
When communicating between modules you can use Shared Services, Commanding, or Event Aggregation. Use the following to help decide which approach to use: