How maven plugin can aggregate information from sub-modules?

I'm trying to develop Maven-3 reporting plugin that will have an aggregate option. When this option is set to true the plugin has collect开发者_运维百科 data from sub-modules and build a report just once - in parent module. How can I do this and where I can find documentation about it? Maybe an example of such a reporting plugin? Pay attention, it's Maven-3.

Take a look at the Maven-JavaDoc-Plugin, the Maven-Source-Plugin and may be the maven-license-plugin but documentation you won't find. The source is the documentation ;-)